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Prison Labor: The Price of Prisons and the Lasting Effects of Incarceration

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Institutions of justice, like prisons, can be used to serve economic and other extrajudicial interests, with lasting deleterious effects. We study the effects on incarceration when prisoners are used primarily as a source of labor using evidence from British colonial Nigeria. We digitized sixty-five years of archival records on prisons from 1920 to 1995 and provide new estimates on the value of prison labor and the effects of labor demand shocks on incarceration. We find that prison labor was economically valuable to the colonial regime, making up a significant share of colonial public works expenditure. Positive economic shocks increased incarceration rates over the colonial period. This result is reversed in the postcolonial period, where prison labor is not a notable feature of state public finance. We document a significant reduction in contemporary trust in legal institutions, like police, in areas with high historic exposure to colonial imprisonment. The resulting reduction in trust is specific to legal institutions today.
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Prison Labor: The Price of Prisons and the Lasting
Effects of Incarceration
Belinda Archibong
Barnard College
Nonso Obikili
United Nations
December 28, 2021
Abstract
Institutions of justice, like prisons, can be used to serve economic and other extra-
judicial interests, with lasting deleterious effects. We study the effects on incarceration
when prisoners are used primarily as a source of labor using evidence from British
colonial Nigeria. We digitized sixty-five years of archival records on prisons from 1920
to 1995 and provide new estimates on the value of prison labor and the effects of labor
demand shocks on incarceration. We find that prison labor was economically valuable
to the colonial regime, making up a significant share of colonial public works expendi-
ture. Positive economic shocks increased incarceration rates over the colonial period.
This result is reversed in the postcolonial period, where prison labor is not a notable
feature of state public finance. We document a significant reduction in contemporary
trust in legal institutions, like police, in areas with high historic exposure to colonial
imprisonment. The resulting reduction in trust is specific to legal institutions today.
JEL classification: H5, J47, O10, O43, N37
Keywords: Prison, Taxation, Convict Leasing, Public Works, Economic Shocks, Trust
Thanks to Stelios Michalopoulos, Nathan Nunn, James Fenske, James Robinson, Liz Ananat, Ebonya
Washington, Eduardo Montero, Nancy Qian, David Weiman, Alan Dye, Marlous van Waijenburg, Suresh
Naidu, Warren Whatley, Lee Alston, Leonard Wantchekon, Michiel de Haas, Denis Cogneau, Rajiv Sethi,
Ewout Frankema, Florence Bernault, Naomi Lamoreaux, Gerald Jaynes, Tim Guinnane, Robynn Cox,
Francesc Ortega, Marcellus Andrews, Claudia Goldin, Owen Ozier, Bryce Steinberg, Ellora Derenoncourt,
Christopher Muller and participants at the NBER and BREAD meetings, the Harvard, Yale, Duke, Brown,
UC Berkeley, Columbia, Queens College, Tennessee, Williams, University of Michigan, and Stanford Eco-
nomics seminars, the SSHA, LACEHA, AEHN, ASA, AEA and other conferences for useful comments and
suggestions. Thanks to Yuusuf Caruso, Monique Harmon, Anamaria Lopez, Robrenisha Williams, Chloe
Dennison, and Serena Lewis for excellent research assistance. All errors are our own.
Corresponding author. Barnard College, Columbia University. 3009 Broadway, New York, NY 10027,
USA. ba2207@columbia.edu.
me@nonsoobikili.com.
1
1 Introduction
“The Prison at Port Harcourt has been considerably developed and at the close
of the year there were 829 prisoners in custody and these are employed by the
Eastern Railway. The Engineer in charge at Port Harcourt is highly pleased with
the way the prisoners are worked; they have given no trouble and have been of
great assistance in developing that station. It was my intention to have 1,000
prisoners stationed there before the close of the year, but this was impossible as
two prisons...which should have supplied the drafts to make up the number, had
an outbreak of chicken-pox...
- E. Jackson, Acting Inspector of Prisons, Lagos, April 23, 1915
There are more people incarcerated today than at any other point in human history1.
The current global prison population is estimated at around 11 million people; rising rates of
incarceration around the world have turned policy discussions to what states should do with
the large reserve of incarcerated people (Jacobson, Heard, and Fair, 2017). One suggestion
that has risen to prominence in recent years in countries such as the US, China, Thailand
and the UK, is to use prisoners for labor in, for example, manufacturing and public works
projects, and to address labor shortages in various industries (Campbell, 2020; Chapman,
2019; Doston and Vanfleet, 2014; Race, 2021; Yuvejwattana and Thanthong-Knight, 2021).
The use of prison labor by governments is not new, although its forms have changed over the
years, with the use of convict labor documented throughout the 19th and 20th centuries as
a feature of European colonial administration in Africa and Asia (De Vito and Lichtenstein,
2013).
Europe’s African colonies, in particular, with their well-documented use of prison la-
1Sources: World Prison Brief and Prison Policy Initiative
2
bor, provide an informative setting to examine the incentive issues that might arise when
prisoners are viewed primarily as a reserve of labor by governments. What are the effects
on incarceration when prisoners are viewed and used as a source of labor to serve economic
interests? And what are the potential implications for populations’ views of state legitimacy,
when an institution of state justice, like prisons, is used to serve economic or extrajudicial
interests? We answer these questions using evidence from British colonial Nigeria, covering a
period between 1920 and 19592, where prison labor was a feature of state public finance and
the labor market; and from post-colonial Nigeria, covering a period between 1971 and 1995,
when prison labor was not a major feature of state finance. We construct a novel dataset
from 65 years of archival records on prisons from 1920 to 1995. We assemble data on prisons,
wages, prices, and colonial public finance from colonial and postcolonial archives, along with
geocoded climate information from high-resolution NASA data to test our hypotheses.
An aim of this paper is to examine how incarceration responds to economic shocks
when prison labor is a major feature of state policy and public finance. To investigate this
topic, we conduct our analysis in three steps. First, we assess the importance of prison
labor by calculating the value of unpaid prison labor, and then estimating the share of
prison labor in colonial public finance. A key insight from the historical archives is that, as
part of explicit colonial policy, prison labor on government public works was a mandated
part of incarceration3. Unpaid prison labor was an essential input in the construction and
maintenance of key revenue-generating public works such as the railroad, which was used
to transport agricultural commodities for export. To the best of our knowledge, we provide
the first set of estimates of the value of unpaid prison labor in British colonial Africa. We
measure the overall value of prison labor as the amount of unpaid wages to prison laborers.
2Nigeria as an amalgamated entity was a British colony from 1914 to 1960. Hence, our dataset covers
almost 40 of the 47 years of the colonial period. The country was under military rule for most of 1960 to
1999, before transitioning to democracy in 1999.
3The 1916 Prison Ordinance outlined the use of convict labor explicitly (Kingdon, 1923).
3
We find that prison labor was economically valuable to the colonial regime. The overall
gross value of prison labor is strictly positive over the entire colonial period. Even after
accounting for the most expansive set of prisoner maintenance costs, the net value of prison
labor is nonnegative and strictly positive in 60% and 57% of the years from 1920 to 1959,
respectively, in Nigeria. Prison labor constituted a significant share of colonial public works
expenditure. The share of overall prison labor in public works expenditure ranged between
40% and 249%, with an average of 101%, over 1920 to 1959. After adjusting for extensive
measures of prisoner maintenance costs, the share of overall prison labor in colonial public
works expenditure remains economically significant, with a mean of 5% and a maximum of
up to 42%, during this period.
Having established the value of convict labor for the colonial regime, next, we assess the
effects of shocks to economic productivity on incarceration, and the use of prison labor using a
panel regression framework. We construct two measures of shocks to economic productivity:
The first measure exploits district-level rainfall deviations in a primarily agricultural setting;
the second measure uses agricultural commodity prices and district-level crop suitability. We
show that the incarceration rate is procyclical during the colonial period. Positive economic
shocks increase the colonial incarceration rate and the use of prison labor. The positive effect
is specific to the short-term incarceration rate only, with temporary shocks increasing the
share of prisoners with sentences fewer than six months. There is no effect of positive shocks
on long-term imprisonment, or the share of prisoners with sentences longer than two years.
In one specification, moderate positive rainfall shocks that raise agricultural productivity
increase the short-term incarceration rate by 16.7 prisoners per 100,000 population, that is,
a 12% increase relative to a mean of 134.7 prisoners per 100,000 population. This effect is
reversed in the postcolonial period wherein prison labor is not a main feature of state policy,
and negative productivity shocks, such as droughts, increase the incarceration rate. Using
an index of export crop prices, we also show that a 1% increase in export prices for a major
4
cash crop in producing regions is associated with a 2% increase in short-term incarceration
relative to the sample mean.
We provide evidence from the historical literature to show that a primary reason for
the procyclical behavior of incarceration rates during the colonial period was increased labor
demand for construction and maintenance of public works like railroads, which were needed to
intensify exports of agricultural commodities during periods of positive productivity shocks.
Labor shortages and tight labor markets, worsened by wage ceilings in the government public
works sector, increased the demand for unpaid prison labor, in line with predictions from
theoretical models of labor coercion (Acemoglu and Wolitzky, 2011). One way colonial
authorities addressed these labor shortages was to increase the share of incarcerated people
by, for example, switching the punishment of certain crimes from fines to imprisonment
(Killingray, 1999). We test the tight labor market hypothesis by examining the effects of
rising wages on the incarceration rate by distance to the colonial railroad. The results show
that, while prisons closer to the railroad have a higher short-term incarceration rate, higher
wages increase the share of short-term prisoners from prisons farther away from the railroad.
The quantitative estimates support historical accounts of prisoners being transported from
prisons throughout districts to work on railroad and other colonial public works projects
during periods of labor shortages (Killingray, 1999).
Finally, to explore the implications of colonial use of prison labor for present-day views
of the state’s judicial legitimacy, we present a brief discussion and suggestive evidence of the
long-run effects of colonial incarceration on contemporary trust in legal institutions. Since
the origins of the modern prison and accompanying legal system in Nigeria and other former
British colonies are rooted in the use of state policy around labor coercion, what are the long-
term effects, if any, of exposure to these systems on populations’ trust in these institutions
today? We use Afrobarometer data from Nigeria on trust in historical legal institutions (e.g.,
5
police, courts, and tax administration) and trust in individuals (e.g., neighbors, relatives, and
the president) to test whether past exposure to coercive, ostensibly economically influenced
colonial prison structures is associated with trust in legal institutions today. We document
a significant reduction in contemporary trust in legal institutions, and police, in particular,
in areas with high historic exposure to colonial imprisonment. The resulting reduction in
trust is specific to legal institutions, with no effect of colonial imprisonment on interpersonal
trust in individuals.
Colonial Nigeria is an informative region to study these issues for a number of reasons.
First, colonial Nigeria had relatively high incarceration rates. As of 1940, the British colonial
government in Nigeria was incarcerating more people (0.3-0.4% in 1940) than countries in
Europe over a similar period (0.06% in 1950)4. In fact, colonial Nigeria was incarcerating
about the same fraction of people as the US prison system was incarcerating its Black
population under the notorious Jim Crow laws of racial segregation over the same time
period, and at a higher rate than the overall US incarceration average of less than 0.2%5.
To put these figures in context with contemporary data, Figure 1 shows the top 40 of 222
countries/jurisdictions by incarceration rate in the world as of 2018. If we place colonial
Nigeria’s incarceration rate in 1940 on the chart, it would have ranked at number 15 of 222
today, right between Seychelles and Panama. Nigeria incarcerates a much lower share of
people today, ranking at around 211 of 222 by World Prison Brief estimates.
We add to several distinct literatures. First, we add to the literature on the economics
of forced labor and coercive labor contracts (Acemoglu and Wolitzky, 2011; Bobonis and
Morrow, 2014; Dell, 2010; Gregory and Lazarev, 2013; Juif and Frankema, 2018; Lowes and
Montero, 2020a; Naidu and Yuchtman, 2013; van Waijenburg, 2018; Saleh, 2019; Dippel,
4Source: Author estimates from archival data and World Prison Brief.
5Colonial Nigeria at a rate of between 0.2-0.4% on average compared to the US Black incarceration rate
of around 0.4% over the same period. Source: (Muller, 2012).
6
Greif, and Trefler, 2020; Sokoloff and Engerman, 2000). Research in this area has examined
the impacts of economic shocks on coercive contract enforcement (Naidu and Yuchtman,
2013), and estimated the share of forced labor in colonial public finance (van Waijenburg,
2018). However, there is very little evidence on the economics of prison labor, with most
research on prison labor concentrated on the United States (Poyker, 2019; Travis, Western,
and Redburn, 2014; Cox, 2010) and the Soviet Union (Gregory and Lazarev, 2013). We
also add to the literature on the economics of incarceration (Becker, 1968; Avio, 1998; Katz,
Levitt, and Shustorovich, 2003). While previous work has focused on the effects of crime
and prison conditions on incarceration rates and recidivism (Becker, 1968; Freeman, 1999;
Bhuller et al., 2020; Katz, Levitt, and Shustorovich, 2003), we highlight the role of economic
shocks in increasing incarceration under coercive state institutions.
There is almost no social science research providing quantitative estimates on the eco-
nomics of prison labor. Of the 95,916 articles on prison labor in the scholarly archive JSTOR,
just 4% are classified in ‘economics’ journals. And of those, only two papers provide quan-
titative estimates on the value and economic drivers of prison labor, with research focused
on estimating the value of British convict labor in 18th century America (Grubb, 2000,
2001). Although there exists a robust, qualitative literature in history, political science, and
sociology on convict labor, previous efforts toward providing quantitative estimates of the
economic drivers of prison labor have been stymied by the paucity of detailed, micro-level
data on incarceration and the value of prison labor. Our study is the first, to our knowl-
edge, to provide quantitative estimates on both the value of prison labor and the effects of
economic shocks on the use of prison labor- particularly when convict labor is a major part
of state policy and public finance- using evidence from extensive archival data.
We also add to a growing literature on the effects of historic, particularly colonial era,
institutions on development outcomes (Lowes and Montero, 2020a; Dell and Olken, 2020;
7
Michalopoulos and Papaioannou, 2016, 2014; Acemoglu and Robinson, 2001). While pre-
vious work has examined the long-run impacts of institutions like the slave trade (Nunn,
2008), colonial labor concessions (Dell, 2010; Lowes and Montero, 2020a; Dell and Olken,
2020) and health (Lowes and Montero, 2020b; Alsan and Wanamaker, 2018) on develop-
ment outcomes, interpersonal trust (Nunn and Wantchekon, 2011; Okoye, 2021) and trust
in modern medicine (Lowes and Montero, 2020b; Alsan and Wanamaker, 2018), our paper is
the first, to our knowledge, to explore the incentive effects of colonial prison labor systems
and their long-term impacts on trust in legal institutions, like police, and views of state
legitimacy. This kind of exploration is needed, particularly in light of research linking en-
vironments of low trust in legal institutions and low views of state legitimacy with conflict
(Rohner, Thoenig, and Zilibotti, 2013), low domestic investment and higher transaction costs
from weak contract enforcement (Knack and Keefer, 1997), as well as issues with effective
policing, crime, and law enforcement (O’Flaherty and Sethi, 2019).
The paper is organized as follows: Section 2 provides historical background on prison
labor in colonial Africa. Section 3 reports quantitative estimates of the value of prison labor
to the colonial regime. Section 4 describes the data on prison labor and economic shocks, and
presents the results on the effects of economic shocks on the incarceration rate and the use of
prison labor. Section 5 discusses the links between colonial imprisonment and contemporary
trust in legal institutions. Section 6 concludes.
2 Prison Labor in Colonial Africa
2.1 A History of Forced Labor
Prison labor was a small part of a larger regime of domestic forced labor in colonial Africa.
European colonial governments were tasked with pursuing strategies to maximize revenue ex-
traction while minimizing the cost of administration in Africa (Gardner, 2012). Attempts to
8
raise revenue to fund expenditures on key public works projects, such as roads and railroads,
which were necessary for both revenue extraction from cash crop exports and expansion
of control of colonies, depended crucially on the colonial government’s ability to raise rev-
enue through direct or indirect taxation, and cut costs associated with expenditures. Labor
shortages were an endemic feature of the African colonies (Okia, 2012; Ash, 2006). Shortages
were driven partly by an unattractive wage labor market for government projects, which it-
self was partly spurred by artificially imposed below-market wage compensation, set both
as a cost-cutting measure and to prevent competition with the private sector, and to sat-
isfy the economic and political demands of white settler employers (Okia, 2012; Maul, 2007;
Ofonagoro, 1982).
To address these constraints, colonial governments enacted a series of strategies to meet
labor and revenue demands. Among these strategies included the use of direct taxation such
as hut and poll taxes requiring cash payment to induce Africans into the wage labor market;
the use of labor tax legislation to force Africans to donate a certain number of hours of
often unpaid labor to private and public sector work; and the use of precolonial communal
labor requirements to compel Africans, under the direction of the chiefs, to provide unpaid
labor for private and public works projects (Okia, 2012; Harris, 1914; Trevor, 1936; van
Waijenburg, 2018; Cooper, 1996).
Forced labor was recognized by the colonial regime as so essential to the functioning of
the state, that, in one instance, when the colonial office in Nigeria surveyed commissioners
in 1911 on their preferences for terminating the House Rule Ordinance, which bolstered the
authority of chiefs to coerce labor for the government, the minutes from the meeting report
that “Perhaps most interesting evidence of all is that of the Commissioners who with one
lament ask how is the administration to be carried out if we cannot go to the Head of a
House and demand carriers and paddlers? How is the work of sanitation, road making and
9
clearing to be carried on if we cannot hold the Head of the House responsible for finishing
the necessary labour? They are all of the opinion that the necessary labour cannot be got,
even at a ruinous price, and that thus the progress and development of the country would
be retarded. (Ofonagoro, 1982), p. 2136. Another important source of forced labor was
convicts.
2.2 Prison Labor in British Colonial Nigeria
Two main reasons for the use of prison labor emerge in the historical literature: First,
prisoners were employed to work as punishment for crimes, as defined by regimes; and
second, the mostly unpaid prison labor was viewed as a source of cheap labor, particularly
for industrial projects in the colonies (Adamson, 1984). Similar crimes did not correspond
to similar punishment- a fact which was often exploited by European colonial governments
to address fiscal pressures and labor shortages7(Branch, 2005; Anderson, 2000).
In British colonial Nigeria, which lasted formally from 1914 to 1960, and throughout
Britain’s African colonies, labor taxes and labor laws worked in concert with Masters and
Servants Ordinances, vagrancy laws, labor registration, pass laws, and Native Authority
Ordinances that mandated the conscription of African laborers to work on colonial public
works projects (Hynd, 2015). Although there is limited disaggregated data on the types of
6Ward-Price, op. cit., p.213. See also CO/520/107, ‘Native House Rule Ordinance’, minutes by Sir Percy
Anderson, 18/12/1911.
7An example of this can be found in an account from British Kenya between 1895 and 1939 where
Anderson (2000) outlines the ways in which a combination of labor demands by the colonial government
and racist views around physical punishment as a ‘necessary evil’ for ‘civilizing’ African populations, led
to differential prosecution of African convicts versus their European and Asian counterparts under alleged
violations of the 1906 Masters and Servants Ordinance. The Ordinance regulated employment contracts
between workers and employers in the region and heavily favored private employers, most of whom were
white European settlers in disputes. Among the possible punishments for violations of the ordinance, which
included ‘desertion’ from work without prior notice, “absence during work hours”, “careless or improper
work” and “using insulting language to the master”, were fines, prison time extending up to 6 months and
whipping (Anderson, 2000), p. 462. Europeans and Asians convicted for breach of the Masters and Servants
Ordinance were much more likely to get fines than prison time or whipping, with Africans more than three
times likely to get prison time than their European counterparts and the only group to be whipped as
punishment between 1931 and 1938.
10
crimes individuals were convicted of, available data from colonial records in Nigeria show
that over 50% of total convictions in colonial courts were from “offences against revenue
laws, municipal, road and other laws relating to social economy of the colony” between 1920
and 1937, as shown in Figure 28. The colonial regime was highly dependent on revenue
from agricultural commodity exports as shown in Figure 39and relied on domestic labor in
facilitating production and exports.
Alongside the growth of coercive laws in the colonies was the increased use of the
prison system and convict labor to work on government public works projects, particularly
in the early part of the 20th century (Hynd, 2015; Akurang-Parry, 2000; Abiodun, 2017;
Bernault, 2007). Individuals who refused, or were unable to pay direct or labor taxes or the
fines associated with non-payment, or committed petty crimes against the colonial regime
or their Native Authorities were arrested and placed in prison; thereafter, their labor was
subsequently exploited for colonial public works projects. An example of this is presented in
accounts by Felix Ekechi (1989) and Stacey Hynd (2015): A sizable number of the inmates
in the Owerri prison in South-Eastern Nigeria were young men who had resisted mandated
labor under the labor regulations. As a result, they were imprisoned and employed as convict
labor on the Eastern Railway. In Nigeria and the Gold Coast, Roger Thomas (1973) notes
that convict labor was often used to manage labor shortages in cash crop production and
mining through the 1920s.
In Nigeria, as of the time of its amalgamation from two separate northern and southern
provinces to a single entity under the governorship of Sir Frederick Lugard in 1914, the
need for cheap labor, combined with the reticence of indigenous workers to work at below
market rate wages on often grueling industrial railroad, road construction, and other public
8Source: British colonial Blue Books, multiple years. There is no disaggregated crime data by the
categories listed in the colonial records between 1940 and 1960.
9This is reversed in the postcolonial regime when revenues from petroleum replace agricultural exports
as the major source of government revenue.
11
infrastructure projects, motivated Lugard to pass the 1916 Prisons Ordinances act giving,
among other things, control of the use of prison labor to the Governor (Kingdon, 1923;
Abiodun, 2017). The Prisons Ordinance, along with the 1914 Native Courts Ordinance, also
outlined the functioning of Nigeria’s dual prison system, with the colonial prisons under the
management of the Director of Prisons and Native Authority Prisons overseen generally by
the local chiefs10 (Kingdon, 1923). Only government agencies were permitted to use prison
labor and prisoners were tasked to work within their provincial districts (Kingdon, 1923;
Abiodun, 2017; Foreign and Office, 1947).
Colonial prisons served a dual mandate. They functioned as centers of control of
African populations as well as a source of cheap labor, allowing the regime to address chronic
labor shortages by providing government administrators with a steady supply of convict
labor (Saleh-Hanna, 2017). So significant was the role of prison labor in the revenues and
expenditures of the colonies, that in 1911, the Governor of Northern Nigeria remarked that
“The value (calculated at 2/3 of the market rate) of prisoners’ labor in connection with
public works, which would otherwise have had to be paid for in cash was 3,878 pounds. If
calculated at the ordinary market rates the value of the prisoners’ useful labor would have
exceeded the entire cost of the Prison Department” (Salau, 2015), p. 323.
Following Lugard’s Order in Council act on July 20, 1916, colonial prisons were clas-
sified into three types: convict prisons, with prisoners serving two or more years to life
sentences, provincial prisons, with prisoners serving greater than six months and less than
two years sentences, and divisional prisons, with prisoners serving less than or equal to six
months sentences (Kingdon, 1923; Abiodun, 2017). Most prisoners were unskilled laborers,
with 65% to 90% of them in provincial or divisional prisons, having short sentences of fewer
10There is little historical information on the functioning of the Native Authority prisons, and we use
records on colonial prisons here. This means the number of prisoners presented here represent only a
fraction of the total number of people imprisoned during this period. We discuss this further in Section 3.
12
than two years, mainly for defaulting on tax payments, and minor offenses like petty thefts
(Hynd, 2015; Report, 1925). Popular departments for the use of prison labor were Public
Works, Railways and Harbors, Native Administration, Police, Public Health and Education,
particularly for short-term prisoners (with sentences less than two years). A robust prison
industry system including bakeries, tailoring, shoe-making, carpentry, printing, and black-
smithing, among others, meant that longer-term prisoners (with sentences longer than two
years) were taught and tasked with learning a trade like carpentry, basket-making, and cloth-
weaving to manufacture furniture and uniforms that could be sold for cash returns that were,
in turn, remitted to the prison department’s funds (Hynd, 2015; Report, 1925). They were
also tasked, as part of the partly punitive, partly “reformatory” motivation of prison work,
with hard labor including activities like stone-breaking and stone-carrying. Prison labor was
reserved exclusively for government use, and colonial officials were careful to choose sectors
for convict labor in order to avoid competing with private industries11 .
Short-term prisoners were tasked with activities like “road construction, street clearing,
grass-cutting, wood cutting, sanitation, conservancy and farm work. Their labor contributed
significantly to public works projects such as quarries in Abeokuta province, coalfields in
Enugu, industries in Lagos, and the Eastern Railway extending from Port-Harcourt in Owerri
province, which used large gangs of prison labor (Abiodun, 2017; Foreign and Office, 1960).
The colonial government was heavily reliant on convict labor, with many of the coal mining
projects and railroad construction work in southeastern Nigeria, for example, through the
early to mid 20th century, being staffed by prison labor (Abiodun, 2017; Foreign and Office,
1960). Under the colonial prison labor system, unpaid prisoners were hired out to other
government departments, who then remitted payment to the prison department for the use
of their labor. To make the system more efficient, prisoners’ labor was classified into unskilled
11Source: “Annual report on the Treatment of Offenders, 1947”.
13
hard labor, skilled hard labor, and light labor12. In Nigeria’s southern provinces, between
73% and 91% of prisoners were engaged in hard or light labor between 1920 and 1937, as
per available data13. Prisoners engaged in hard labor alone constituted over 70% of convicts
over the same period. The vast majority of prisoners had to work, usually on public works
projects like roads, railroads, building construction, and in the mines14.
The recruitment of prisoners for labor was also stated explicitly by colonial officials, as
illustrated in Abiodun (2017)’s account of the response of colonial government officials to a
request for increased funds for the employment of wage labor by a British sanitary inspector
in 1923: “The officials asked the prison department to find ways to either increase the prison
population or recruit convicts from outstation prisons to complete the tasks.15. In another
example, the Inspector of Prisons, W.H. Beverley, in the 1916 Annual Report on Prisons lists
two main reasons for creating categories of prisons according to prison sentence as (a) to place
‘special prisons’ in “townships which are on good lines of communication and afford the most
suitable description of penal labour. (Abeokuta, Enugu, Lagos, and Port Harcourt, on the
eastern and western lines of the Nigerian Railway, provide quarrying, industrial work, labour
connected with shipping and transport, etc.)” and (b) “the ensuring, as far as possible, of an
automatic and constant supply of prisoners to each class of prisons. At the end of the year,
the system appeared to be working well; the long and medium sentence men were in the
12Source: British Blue Books, Nigeria, multiple years. Other similar classifications included “industrial
labor, domestic labor and unskilled labor”, where ‘domestic labor’ was considered light labor and industrial
and unskilled labor were considered hard labor. Unskilled hard labor included work for which “no training
was needed”, with examples given including “coaling ship, grass-cutting, painting and refuse disposal”.
Skilled hard labor included work for which “special training was necessary” including jobs like “basket-
weaving, brick-making, carpentry, clerical work, cooking, laundering, mat-making, masonry and tailoring”.
Light labor consisted of “easy duties suitable to the bodily or mental infirmity of the prisoner” including
“cell-cleaning, lamp-trimming, sweeping and preparation of foodstuffs for cooking”’ (Foreign and Office,
1960).
13Between 9% and 26% of prisoners were considered ‘unfit’ for work either due to being non-sentenced
debtors or other not yet sentenced individuals in custody awaiting trial or being too sick to work. Source:
British Blue Books, Nigeria, multiple years.
14Source: British Blue Books, Nigeria, multiple years.
15NAI, CSO 26/2 09591 Vol.1 ‘Lieutenant Governor Southern Province to Resident Calabar Province:
Memorandum on Prison labor’ 23rd April 1923.
14
prisons appointed to retain them, the prison population was evenly distributed, and nowhere
was there shortage of convict labour.” (Foreign and Office, 1960).
The practice of prison labor in Nigeria continued sporadically through the 1950s, and
ended prior to Nigeria’s independence in 1960, under increasing protest from local anti-
colonial groups and labor unions (Killingray, 1999; Abiodun, 2017). Section A.2 in the
appendix provides more detail on the history of prison labor in British colonial Africa.
3 Estimating the Value of Prison Labor
3.1 Historical Data
To assess the significance of unpaid prison labor for colonial public works expenditures, or the
value of prison labor, we digitized archival records on the prison population, wages, public
works expenditure, and revenue from the British colonial Blue Books and Annual Report on
the Administration of the Prisons Department16 between 1920 and 1959. The Blue Books
were statistical returns that governors of British dependencies were required to submit on
an annual basis and report a complete record of prisons and colonial public finance between
1920 and 1938 in Nigeria17. The Blue Books and the Annual Report also include qualitative
descriptions of the activities undertaken by prison departments, as reported by the Director
of Prisons. An example of the archival data is shown in Figure 4. These data sources and
the variables we use in our analysis are described in detail in Appendix A.1.
Figure 5 shows maps of Nigeria with its colonial provinces, regions, and prison locations
labeled, including the extent of the colonial railroad. We note an important point here: The
16Referred to as the Annual Report subsequently.
17Nigeria is amalgamated from separate regions into a single country in 1914 and although the Blue Books
data extend back to 1914, some information is missing between 1914 and 1920, so we start our analysis in
1920 for completeness. The Blue Books data on prisons and public finance ends in 1938. For prison data
after 1938, we use records from the Annual Report on the Administration of the Prisons Department.
15
colonial prisons data represent only a fraction of the overall prison population in Nigeria.
There are no detailed data on Native prisons administered by local chiefs in the colonial
archives prior to 1940. Available data on Native prisons in the Annual Reports from 1940
show that the addition of Native prison estimates to the colonial estimates presented in
this paper would almost double the incarceration rate in 1940 from around 224 per 100,000
population to 399 per 100,000 population. This suggests that the data we present here from
1920 to 1959 may be an underestimate of the total level of incarceration during this period.
There are also clear differences in the distribution of colonial prisons by region. Of the 48
prisons recorded in 1938, about 90% are located in the southern provinces. The map is
reversed for Native prisons, with just 13% of Native prisons, that is, 9 of 65 recorded in
1940, located in the southern provinces, as shown in Figure A2 in the Appendix. Historical
differences in the level of precolonial state bureaucracy drive differences in the geographical
distribution of Native versus colonial prisons (Archibong, 2019)18. Using the available data
from colonial prisons, we present results here as lower bound estimates on the total value of
convict labor over this period.
3.2 Empirical Strategy
We measure the value of convict labor to the colonial regime by adapting the strategy from
van Waijenburg (2018) to estimate the value of unpaid prison labor, and its relative share in
expenditure on new construction of colonial public works19. In essence we ask, “How much
would the colonial state have had to pay if they had to hire non-remunerated prison workers
for a market rate wage?”
18Appendix A.3 presents a brief discussion of the historical drivers behind these differences. See Archibong
(2019) for a more in-depth discussion.
19We use expenditure on new public works construction only here as a comparison as it reflects value-
adding investment in productive public works rather than just upkeep or maintenance. New expenditure
represents about 40% of total, new and maintenance, public works expenditure between 1920 and 1959.
In Appendix A.4.3, we compare the value of prison labor figures to total public works spending, including
recurrent expenditure on regular maintenance of public works reported in the archives.
16
We calculate the overall value of unpaid prison labor in each year tas:
Value of prison labort=Annual wagest×
N
X
n=1
Prisonersnt (1)
This gives us an overall gross value of benefits accruing to government consumers of
prison labor. As a measure of wages, we use the average annual market wages paid to
unskilled laborers. This captures the wages for some of the types of work that prisoners
were required to perform, including felling trees and breaking rocks to clear areas for road
construction, as discussed in section 2. P risonersnt is the daily average number of people
in prisons over ndays in the year from the archival records. This measure captures the
amount of convict labor that was available on any given day. To estimate the relative value
of prison labor, we divide the results from Equation 1 by public works expenditures, prison
expenditures and overall expenditure figures from the Blue Books.
The specification in Equation 1 does not factor in the costs of prisoner maintenance,
including food, clothing, and prison staff salaries. The archival data report two sets of costs
for prison maintenance: (i) food costs, which is reported as the main cost of prisoner upkeep;
and (ii) total prisoner maintenance costs, an estimate that divides all expenses involved in
operating the prison (i.e., everything from staff salaries to equipment purchases) by the total
number of prisoners in a given year. Food cost is for an average of 35% of the total prisoner
cost for 1920-1959, and ranges from 27% to 51% of the total cost over the study period. Food
cost and staff salaries account for over 50% of the total prisoner cost from 1920 to 1959. The
total prisoner maintenance cost is the most expansive measure of the prison upkeep cost.
We present the results on the net value of prison labor using both the food and the total
prison maintenance costs in section 3.3.
Figure 6(a) shows the trends in the reported average annual wage and prisoner food
17
and overall maintenance costs. The total reported prisoner upkeep cost closely tracks the
wage, reflecting increases in staff salaries over time, with a steep increase after 1940. Prisoner
food cost follows a similar pattern, although the post-1940 increase in cost is less steep than
the wage and total prisoner cost. Figure 6b shows the daily average number in prison over
the study period. The wage is above prisoner food costs in all years, and above total prisoner
costs in over 51% of the years between 1920 and 1959. The daily average number in prison
fluctuates notably between 1920 and 1940, increasing through 1930, then decreasing between
1930 and 1940, before sharply increasing after 1943. Interestingly, the daily average number
in prison also appears to track the average annual wage in Figure 6a20 .
We estimate various versions of Equation 1 in alternate specifications, including esti-
mates using alternate wage measures, adjusting for inflation, and addressing any potential
bias in prisoner estimates by computing a weighted average measure of people committed
to prison for penal imprisonment in each year. The trends in the results remain unchanged
and are detailed in Appendix A.4.
3.3 Value of Prison Labor Results
Figure 7(a) and Table A2 in Appendix A.4 report our imputed total and net value of prison
labor results. The total gross value of prison labor starts out around 178,498 pounds in 1920
and fluctuates- first decreasing, and then increasing through 1927, before mostly declining
through 1943, then increasing sharply afterwards, peaking at 1,532,634 pounds in 195921 .
The average gross value of prison labor is 313,742 pounds over the colonial period. We
observe similar trends with the net value of prison labor, less prisoner food costs; the net
value of prison labor less food costs remains strictly positive over the study period with
20The correlation between the daily average numbers in prison and the average annual wage to unskilled
laborers is 0.87, p < .001.
21Given the debates around the choice of the price index for colonial Africa, we present the figures in
nominal terms here (Frankema and Van Waijenburg, 2012). We present the real estimates in Appendix A.4.
The trends remain unchanged.
18
the average falling to 195,260 pounds. When we estimate the net value of prison labor
using the most expansive measure of prisoner maintenance costs reported, the mean falls
further to 31,674 pounds. The net value of prison labor, subtracting total reported prisoner
maintenance costs from the gross value of prison labor, is nonnegative and strictly positive
in 60% and 57% of years respectively over the colonial period in Nigeria.
To evaluate the significance of the prison labor value for colonial public finance and
spending on public works, the major category prison labor was employed on, we estimate the
ratio of our prison labor values to reported new public works expenditure. We also compare
the prison labor values to overall prison expenditure and overall expenditure by the colonial
government. Figure 7(b) and Table A2 report the estimates for the share of prison labor
in public works expenditure from 1920 to 1959. The share, using the gross value of labor
coercion, fluctuates throughout the colonial period; it starts out at 133% in 1920, and then
declines through 1932, before increasing through 1936 and again declining through the 1940s.
The prison labor share in public works expenditure increases sharply after 1943, peaking in
1952 and 1953 at 249%, before declining through 1959. The share of overall prison labor in
colonial public works expenditure ranges between 40% and 249%, with an average of 101%
over 1920 to 1959. After adjusting for extensive measures of prisoner maintenance cost,
the share of overall prison labor in colonial public works expenditure remains economically
significant, with a mean of 5% and a maximum of up to 42% during this period.
We show similar trends for the prison labor share of total prison expenditures and over-
all colonial expenditures over this period in Figure 7(c) and Figure 7(d), respectively. Given
the relatively small share of new public works expenditure in overall colonial spending22,
the prison labor share in the overall colonial expenditure is low, constituting an average of
2% and 0.1% of total expenditure, using the gross and net values of prison labor (includ-
22An average of 2.2% between 1920 and 1959.
19
ing total prisoner maintenance costs), respectively. The results show that prison labor was
economically valuable to the colonial regime.
3.3.1 Comparing Imputed Estimates of the Value of Prison Labor to Reported
Colonial Estimates
As a specification check, we compare our estimates of the value of prison labor to the colonial
government’s own estimates of the value of prison labor, shown in Figure 7(a) and Table
A2. In some years, the colonial authorities published their own estimates of the total value
of prison labor in Nigeria. Prisoners were most often hired to the Public Works and other
government agencies for labor. Although the prisoners were not paid, payment was remitted
directly from these agencies to the prison department for prisoners’ work. The prison depart-
ment then had to set prices for their prisoners’ work for other government agencies. These
prices are explicitly listed as their estimates of the “value of prison labor” in the Annual
Reports23 .
We compile these estimates where available, and they provide us with comparable
data from 1919 to 1925. Figure 8 shows our estimates of the difference in the daily market
wage rate versus the prison rate in the Lagos colony and southern provinces for laborers
or unskilled hard labor and for “carpenters and joiners” and “bricklayers and masons”, two
classes of skilled hard labor. Lacking data past 1921 on the per diem prison rates, we assume,
based on the past record, that the rates remain stable through 1925. As shown in Figure
23The Directors of Prisons, for example, W.H. Beverly, E. Jackson or W. Reeder in the southern provinces
over 1915 to 1921, recorded per diem estimates of the value of labor between 1916 and 1921 in the Lagos
colony and southern provinces for Nigeria. Using the classification of labor into skilled hard labor, unskilled
hard labor and light labor, described in Section 2.2, hard labor, both unskilled and skilled are given a value
of 5 pence per day, with light labor given a value of 3 pence per day in 1916. Starting in 1917, skilled hard
labor is given a value of 1 shilling and 6 pence or 18 pence, unskilled hard labor is assigned a value of 5
pence and light labor is assigned a value of 3 pence. The rates for unskilled hard labor stay the same from
1918 through 1921, with no reporting on the exact value assigned to skilled hard labor or light labor over
this time. After 1921, the reports stop including information on the per diem value assigned to the different
classes of labor.
20
8, prisoners performing unskilled hard labor, which made up the majority of the prison
population (prisoners with shorter-term sentences), were assigned a value between about
60% to 80% below the market wage rate over 1919 to 192524 . Our measures of the value of
prison labor are higher than the estimates of the colonial authorities; colonial prison officials
were consistently undervaluing prisoners’ labor to keep administration costs for their peer
departments low while attempting to balance their budgets.
4 Effects of Economic Shocks on Incarceration Rates and the Use
of Prison Labor
4.1 Data on Incarceration Rates and Economic Shocks
Given the economic significance of prison labor for colonial public works discussed in section
3, to understand the effects of economic conditions on the use of prison labor, we examine
the effects of economic shocks on incarceration rates over the colonial period. Our outcome
of interest, incarceration rates, is only available in disaggregated form during the colonial
period from 1920 to 1938, and we limit our analysis to these years for the colonial era. The
Blue Books report imprisonment data at the prison level, and we aggregate up to the district
level, where the district is the colonial province between 1920 and 1938; we calculate the
incarceration rate as the number of newly admitted prisoners per 100,000 population for
each province in each year.
The imprisonment data are broken down by length of prison sentence, classified as
short-term (less than six months), medium-term (between six months and two years) and
long-term (greater than two years) prisoners. We use this classification of sentences for falsi-
24This confirms the report written by Beverley himself in the 1915 Annual Report on Prisons where he
states that values assigned to prisoners’ labor is below “wages demanded by workmen in civil life”. He
recommends a doubling of values to balance prison expenditure amounts, illustrating the balance sheet
calculus that appeared to drive the setting of values of prison labor.
21
fication tests in order to test the hypothesis that yearly variation in economic shocks should
affect short-term prisoners, whose populations are more elastic than long-term prisoners.
As an additional falsification test, and to test the hypothesis presented in Section 1 and
Section 2 that the impacts of shocks on incarceration should differ between the colonial and
postcolonial period due to differences in the economic structure and state policy regarding
incarceration between the two periods, we use available data on postcolonial incarceration
rates at the current administrative state level between 1971 and 1995 from Nigeria’s Annual
Abstract of Statistics25.
To measure economic shocks, and test the hypothesis presented in the introduction that
positive shocks will increase incarceration rates under a regime that uses prison labor to serve
economic interests, we use two sets of data. Since our setting is primarily agricultural26, we
can measure shocks to economic productivity using data on rainfall and agricultural com-
modity export prices. First, we use rainfall data from 69 weather stations recorded in the
Blue Books to construct measures of rainfall deviations, or z-scores, as deviations from the
province long-term mean. We use this to estimate the effects of rainfall shocks on incarcer-
ation rates27. For our falsification test in the post-colonial period, we use precipitation data
from the NASA MERRA-2 database28.
Second, we estimate the effects of productivity shocks on colonial incarceration rates
using export crop price data on the major cash crop exports in colonial Nigeria, which include
cocoa, palm oil and groundnuts; the data are from the Wageningen University African Com-
25The postcolonial data does not include breakdown by sentence.
26The share of agriculture in GDP has ranged between 40% and 60% between 1960 and 2012 by some
estimates (Ahungwa, Haruna, and Abdusalam, 2014).
27In alternate specifications, we test results with interpolated data from the University of Delaware
database, and confirm that while there is a significant positive correlation between the rainfall values, the
correlation is low and does not translate to the z-scores which are the main explanatory variable used here.
Given that the Delaware values from 1920 are less fine interpolations than the weather station data, we use
the weather station data here for our main results.
28The NASA MERRA-2 data is not available prior to 1980.
22
modity Trade Database (Frankema, Williamson, and Woltjer, 2018). We combine the price
data with land suitability and crop production data from the Global Agro-Ecological Zones
and Blue Books databases, respectively, to identify which prices would have theoretically
affected which districts.
4.2 Summary Statistics
Table 1 presents the summary statistics. The average incarceration rate falls by almost a
third between the colonial and postcolonial periods from around 241 prisoners per 100,000
people to 92, respectively, as shown in Table 1 and Figure 9. The spatial distribution of
incarceration between the colonial and postcolonial period also changes significantly, with
prisoners being clustered in the southern provinces over the colonial period, and significantly
more spatial dispersion in the postcolonial period, as shown in Figure 10. Incarceration rates
are also higher, on average, in the southern provinces, at 216 prisoners per 100,000 population
versus 19 prisoners per 100,000 population in the northern provinces29. Trends in overall
colonial incarceration rates track the trends in southern incarceration rates, as shown in
Figure 11.
Short-term prisoners make-up the vast majority of the colonial prison population at
58% of all newly committed prisoners and 84% of penal imprisonment, on average, between
1920 and 1938, as shown in Table 1. The share of long-term prisoners in penal imprisonment
is comparatively smaller, at 5% over the same period. The share of prisoners with previous
convictions is similarly low, with 11% of prisoners having one previous conviction and only
2% of prisoners with two or three previous convictions.
29Although we do not have detailed data on Native prisons, data provided from the colonial archives for
2 years, 1940 and 1945, show similar north-south trends in Native incarceration rates as shown in Figure
A3 in Appendix A.3. From Figure A3, incarceration rates are higher in a southern province, Oyo, than in
the northern provinces on average. The southern Native prisons, for the available data in the 1940s, also
incarcerate more people than their northern counterparts on average, following the trends in the colonial
incarceration data. Average incarceration rates in Native prisons between 1940 and 1945 (181 per 100,000
population) are slightly higher than in colonial prisons (130 per 100,000 population) over the same period.
23
Figure 12 shows the spatial distribution of cash crop production over the colonial
period. Palm oil and cocoa are produced in the southern provinces, while groundnut is the
major cash crop export produced in the northern provinces. The time series of export cash
crop prices are shown in Figure 11. Prices for cash crops in the southern provinces, namely
cocoa and palm oil, are 2 times and 1.5 times higher, on average, than prices for groundnut
produced in the northern provinces over 1920 to 1938. After an initial decline in 1920, these
prices remain relatively stable through 1930, before there is a sharp Depression-era drop
in export prices from 1935 onward. They start to rise again briefly before another decline
toward the end of 1938.
4.3 Estimating Equations
To examine the effects of shocks to economic productivity on incarceration rates and the
use of prison labor in the colonial period, we use three estimating equations: (1) a nonlin-
ear, quadratic specification that allows the effect of rainfall shocks on incarceration to vary
more flexibly with the level of district-level rainfall deviation, and estimates the effects of
positive productivity shocks on incarceration rates; (2) a linear specification that identifies
the effects of moderate positive rainfall shocks, in particular, on incarceration; and (3) a
linear specification that identifies the effects of productivity shocks with an interaction term
for agricultural export commodity prices. We include district (province or current state for
colonial or postcolonial data respectively) and year fixed effects in all specifications, along
with clustered standard errors at the district level. Following Cameron, Gelbach, and Miller
(2008), we apply wild bootstrap-based tests to our estimates to account for potentially low
numbers of clusters in estimating our standard errors, and include wild cluster bootstrap
p-values in our results. The rationale behind each empirical strategy is discussed in further
detail in the proceeding sections. Our main specifications will be related models (1) and (2),
although we interpret the results from all three models in section 4.4.
24
4.3.1 Nonlinear Effects of Economic Shocks on Incarceration Rates
Following the discussion in section 1 and section 2, positive rainfall and agricultural com-
modity price shocks that boost economic productivity may increase incarceration rates by
increasing prison labor demand for construction and maintenance of public works like rail-
roads, needed to intensify exports of agricultural commodities during periods of positive
productivity shocks
Colonial officials push forward construction and intensify maintenance on public works
like roads and the railroad, but facing severe labor shortages due to the increased relative
value of African laborer/farmer outside options during periods of heightened agricultural
productivity, switch the prosecutions/sentencing of certain crimes to short-term prison sen-
tences to better use unpaid prison labor. This is partly reflected in Figure 2, which shows
that the majority of crimes leading to imprisonment are “crimes against the colonial econ-
omy” (e.g., tax default). Our hypotheses here are that (a) the main functional form of
the relationship between rainfall shocks and incarceration rates in the colonial period is an
inverted-U. The demand for prison labor peaks during periods of moderate positive rainfall
shocks which reflect increases in agricultural productivity. In contrast, extremes in rainfall
deviations like droughts and floods which lower agricultural productivity lower the demand
for prison labor. As a falsification test, these effects should only hold for short-term incar-
ceration, which is more elastic and should be more responsive to short-term economic shocks
than long-term imprisonment.
A testable implication of (a) is that, (b) as a falsification test, the effect of rainfall
shocks on incarceration rates be U-shaped during the colonial period if a major motive for
state incarceration was not prison labor. Under a non-convict labor motivated prison system,
droughts and floods that lower agricultural productivity should increase incarceration rates
through a rise in economic crimes like theft, in line with past theory and evidence from the
25
crime literature (Becker, 1968). Incidentally, “offences against property” or property theft is
the major category of prison convictions over the postcolonial period, as shown in Figure 2.
The nonlinear relationship between rainfall and agricultural output has been high-
lighted in the literature (Lesk, Rowhani, and Ramankutty, 2016; Kaur, 2019; Sarsons, 2015).
We can then estimate the causal effect of rainfall shocks on incarceration rates by assessing
panel regressions of the following nonlinear, quadratic form:
Prisonersit =β1RainfallDevit +β2RainfallDev2
it +µi+δt+it (2)
where P risonersit is the incarceration rate or number of newly committed prisoners
per 100,000 population30 in district iat year t; RainfallDevit is the rainfall deviation or
z-score for each district in each year relative to the district’s long-term expectation31 ;µiand
δtare district and year fixed effects respectively. Errors are clustered at the district level
to allow for arbitrary correlations32. Our key parameter of interest is β2which should be
significantly negative if hypothesis (a) above holds and positive if hypothesis (b) holds.
Given the different shares of Native to colonial prisons and prisoners in the northern
(more Native, less colonial prisons) versus southern (more colonial prisons and prisoners)
provinces, and the implications of those shares for how prisoners were used for prison labor,
as discussed in section 2, our third hypothesis is that (c) the positive effect of agricultural
productivity enhancing rainfall shocks on incarceration rates should hold more strongly in
the southern provinces than in the northern provinces over the colonial period. To test
hypothesis (c), we examine heterogeneity in the effects of Equation 2 by region.
30The results remain unchanged if we standardize by the adult population only.
31We find no effects when we test the specification using lagged rainfall deviations instead following results
in previous literature (Amare et al., 2018).
32We estimate all models with standard errors clustered at the district level and Conley standard errors
with a cut-off window of 100 km to account for spatial auto-correlation (Conley, 1999). The results are
robust to both specifications, and we present the district level clustering results here.
26
4.3.2 Identifying the Effects of Positive Rainfall Shocks on Incarceration Rates
While Equation 2 allows us to more flexibly identify the effects of rainfall shocks on incarcer-
ation rates and the use of colonial prison labor, it does not allow us to distinguish between
positive and negative rainfall and productivity shocks. Specifically, Equation 2 does not
allow us to distinguish between moderate positive rainfall shocks that signal increases in
agricultural productivity, and extreme positive and negative shocks that respectively signal
floods and droughts that can reduce productivity.
A problem that arises when trying to distinguish between positive and negative shocks,
and identify moderate positive rainfall shocks from droughts and floods, is that the classifica-
tion is often highly dependent on the particular regional context/climate, and, as mentioned
previously, the relationship between rainfall and agricultural output is often non-linear (Lesk,
Rowhani, and Ramankutty, 2016; Sarsons, 2015; Kaur, 2019; Amare et al., 2018; Jensen,
2000). Additionally, while there is a robust literature on rainfall shocks and agricultural
productivity in South Asia, there is relatively little research on the links between rainfall
shocks and productivity in West Africa (Amare et al., 2018; Papaioannou and de Haas, 2017;
Dillon, McGee, and Oseni, 2015; Jensen, 2000).
Since we do not have data on agricultural output from the colonial period, we adapt
definitions of rainfall shocks in Africa from the literature (Dillon, McGee, and Oseni, 2015;
Amare et al., 2018; Jensen, 2000) and estimate transition points in Equation 2 from non-
parametric loess models linking rainfall deviations to colonial incarceration rates. From the
transition points, we distinguish between moderate positive shocks, extreme positive shocks,
and extreme negative shocks as follows: (a) Positive shock (M), where ‘M’ is moderate, is
an indicator equal to 1 if 0 < Rainf allDevit <0.75 and a proxy for increases in agricul-
tural productivity; (b) Positive shock (E), where ‘E’ is extreme, is an indicator equal to 1
if RainfallDevit >0.75, and signifies floods that reduce agricultural productivity and (c)
27
Negative shock (E), is an indicator equal to 1 if RainfallDevit <0.5, and signifies droughts
that also reduce agricultural productivity.
We can then directly estimate the causal effect of moderate positive rainfall shocks on
incarceration rates by estimating the following linear specification:
Prisonersit =αPositive shock (M)it +µi+δt+it (3)
where Positive shock (M)it is the moderate positive rainfall shock and other variables
are as defined in Section 4.3.1. The main parameter of interest in Equation 3 is α, defined as
the effect of moderate positive shocks that increase agricultural productivity on the incarcer-
ation rate. In alternate specifications, we include the extreme positive and negative rainfall
shock variables to check the robustness of our results. We also examine heterogeneity by
southern and northern province, and examine the effects of positive shocks on postcolonial
incarceration rates, repeating the heterogeneity and falsification exercises in Section 4.3.1.
Although we do not have disaggregated data on crime, to test the ‘sentence-switching
as a way to increase the share of short-term prisoners for prison labor in response to positive
economic shocks’ hypothesis mentioned in section 4.3.1, we estimate Equation 3 using the
difference between custody/awaiting trial and short-term incarceration figures as an outcome.
The rationale here is that, given that only sentenced prisoners could legally be used for prison
labor, if there is more sentence switching from ‘awaiting trial’ to short-term imprisonment
in response to positive economic shocks, αwill be significantly negative for the difference.
4.3.3 Effects of Cash Crop Price Shocks on Colonial Incarceration Rates
As a robustness check, following the literature on commodity price shocks and agricultural
productivity (Dube and Vargas, 2013; Naidu and Yuchtman, 2013), we examine the effects
28
of plausibly exogenous agricultural export price shocks, signaling increases in agricultural
productivity, on colonial incarceration rates and use of prison labor. We estimate equations
of the following form:
Prisonersit =
3
X
c=1
γcCash Cropci ×Cash Crop Pricect +µi+δt+it (4)
where Cash Cropci is an indicator that equals 1 if province iproduces one of the
3 major export cash crops c (cocoa,palmoil,groundnut)over the colonial period, and
Cash Crop Pricect is the natural log of the export price of cin year t. The coefficient of
interest is the interaction term γcwhich measures the effect of increases in cash crop prices
in producing provinces on the incarceration rate.
The railroad was an important capital input in colonial revenue production functions,
given its importance in the transport of cash crops for export (Okoye, Pongou, and Yokossi,
2019). A major use of prison labor was for public works and railroad construction and
maintenance as discussed in section 2 and shown in section 3. As an additional specification
check, we examine the effects of increases in nation-wide wages on colonial incarceration
rates by distance to the railroad. The wage time series measure interacted with distance
from each prison to the railroad, gives us a proxy for labor market tightness and allows us
to test if a tighter labor market intensifies the demand for prison labor, as reflected in the
colonial incarceration rate around the railroad.
4.4 Results
4.4.1 Nonlinear Effects of Economic Shocks on Incarceration Rates Results
To examine the causal effect of economic shocks on incarceration rates, we first present the
results using the rainfall deviation measures in Equation 2 in Table 2. While the quadratic
29
term is negative but not significant when we examine all penal imprisonment over the colonial
period in column (1), the effect is significant and negative for short-term incarceration rates.
The negative quadratic coefficient for short-term incarceration is consistent with an inverted-
U relationship between rainfall deviation and short-term imprisonment or the use of prison
labor. β2, the squared rainfall deviation term is not significant for medium or long-term
incarceration rates, in line with the predictions in section 4.3.1.
The results of the falsification test for postcolonial imprisonment are shown in column
(5) of Table 2. β2from Equation 2 is positive and significant for postcolonial incarceration
rates. The positive significant estimate for postcolonial incarceration is consistent with hy-
pothesis (b) from section 4.3.1 that the effects of rainfall shocks on incarceration rates should
be U-shaped when prison labor is not a major feature of state policy; instead, imprisonment
increases primarily as a response to increases in economic crimes like theft in the aftermath
of negative productivity shocks (e.g., drought or floods).
Table 3 reports the results when we examine heterogeneity by southern and north-
ern province. β2is negative and significant for short-term imprisonment in the southern
provinces, but positive and significant for northern provinces, following the discussion in
section 3. Given the relatively higher share of Native Administration prisoners in the north-
ern provinces, one explanation for the reversal is that colonial prisons in the North held
fewer prisoners than their Native counterparts. Northerners may have been more likely to
be incarcerated in colonial prisons after committing crimes that were specifically targeted
against Europeans or non-African natives, such as theft or violations of the aforementioned
colonial economy laws (Killingray, 1999; Bernault, 2007).
So while there existed prison labor in both regions, the colonial prisons in the south-
ern provinces, being the only arm of the prison system for most southern provinces33 are
33There are 56 Native prisons in the Northern provinces vs only 9 in the South, and concentrated entirely
in the southwest region as of 1940 as shown in Figure A2.
30
used more intensely for prison labor in response to labor demand shocks than their northern
colonial prison counterparts. Consistent with the hypothesis that there should be no effect
of yearly economic shocks on long-term prisoners, we see no effect for this category, disag-
gregated by region in Table 3. Consistent with the inverted U-shaped hypothesis, moderate
positive rainfall shocks increase short-term imprisonment and the use of prison labor, par-
ticularly in the southern region, where colonial prisons were often the only source of prison
labor.
4.4.2 Identifying the Effects of Positive Rainfall Shocks on Incarceration Rates
Results
Table 4 reports the results from Equation 3, which identifies the effects of moderate positive
rainfall shocks that raise agricultural productivity, versus extreme positive or negative rainfall
shocks (respectively signifying floods or droughts that reduce productivity) on incarceration
rates. The results from our main specification in column (1) show that moderate positive
rainfall shocks have a significant positive effect on short-term imprisonment over the colonial
period. A moderate positive rainfall shock increases the short-term incarceration rate by
16.7 per 100,000 population, or around 12%, relative to the sample mean of 135 per 100,000
people. The effect remains significant, increasing the short-term incarceration rate by about
9% when we add controls for extreme negative and positive rainfall shocks in column (3) of
Table 4.
In line with the inverted U-shape prediction, column (2) and column (3) of Table
4 show the opposite result for extreme negative rainfall shocks, which reduce short-term
colonial imprisonment. Extreme negative rainfall shocks like droughts signal a decrease in
agricultural productivity and decrease demand for unpaid prison labor under the colonial
system; this is reflected in the lowered incarceration rates, with extreme negative rainfall
shocks associated with a 13% to 15% decline in short-term incarceration relative to the
31
sample mean. There are no effects of rainfall shocks on long-term incarceration, as shown in
columns (4) to (6).
In contrast, the postcolonial results show that, while moderate positive rainfall shocks
have no significant effect on postcolonial incarceration rates (column (7) and column (9)),
extreme negative (column (8)) and extreme positive (column (9)) rainfall shocks increase the
postcolonial imprisonment rate. From column (9), the magnitude of the increase in post-
colonial imprisonment from droughts/extreme negative rainfall shocks and floods/extreme
positive rainfall shocks is a 21% and 19% increase in incarceration rates relative to a sample
mean of 105 per 100,000 people. The linear specification results are consistent with the re-
sults from the quadratic specification in Equation 2 showing an inverted U-shape relationship
between rainfall deviation and incarceration rates in the colonial era, with a reversal/U-shape
relationship in the postcolonial period.
Table 5 reports estimates from the heterogeneity by region analysis, and confirms
the results from section 4.4.1. The positive relationship between moderate positive rainfall
shocks and colonial incarceration rates is driven by short-term incarceration in the southern
provinces.
Table A4 in Appendix A.5 provides suggestive evidence of ‘sentence-switching’ as a
strategy to increase the share of short-term prisoners for prison labor in response to positive
productivity shocks. While the specifications in columns (1) to (4) confirm a positive, mostly
significant relationship between moderate positive rainfall shocks and both ’custody/awaiting
trial’ and short-term incarceration rates, the effect of shocks on their difference, in columns
(5) and (6), is negative. Given that the coefficients on both custody and short term incar-
ceration rates are positive, the only way for their difference to be negative is if short-term
incarceration is rising faster than custody sentences in response to moderate positive rain-
fall shocks. One interpretation is that people may have been transferred at a faster rate
32
from custody/awaiting trial to short-term sentences so that the state could take advantage
of unpaid prison labor when moderate positive rainfall shocks increased labor demand and
worsened labor shortages. The αcoefficient is not robust to the inclusion of the other rainfall
shock terms, as shown in column (6), and should be interpreted with caution, but provides
suggestive evidence of the switching hypothesis.
4.4.3 Effects of Cash Crop Price Shocks on Colonial Incarceration Rates Results
Table 6 presents the results from Equation 4. The results show that the effect of plau-
sibly exogenous positive agricultural export price shocks signaling increases in agricultural
productivity on colonial incarceration rates and the use of prison labor is concentrated in rel-
atively higher value cash crops, like palm oil, which are produced in the southern provinces.
We interpret the coefficients from the full specification of the model in column (1), with
short-term incarceration rates as the outcome of interest.
A 1% increase in palm oil prices in palm oil producing regions is associated with an
increase in the short-term incarceration rate by around 3 per 100,000 people, a 2% increase
in short-term incarceration relative to the sample mean. Short-term incarceration rates
are elastic and responsive to increases in palm oil prices, signaling increases in agricultural
productivity. The effect is strongest for palm oil-producing regions in the southern region
where colonial prisons are the only source of unpaid prison labor, in the absence of Native
prisons. There is no effect of the palm oil price interaction on long-term incarceration
rates in column (5). Note that, for almost all cash crops in column (1) and column (2),
colonial production of the crop is significantly, positively associated with both short-term
and long-term incarceration. There were more colonial prisoners, on average, in provinces
with cash crop production. The positive effects of cash crop production on short- and
long-term imprisonment are particularly robust for palm oil producing areas, based on the
bootstrapped p-values.
33
4.4.4 Railroad, Wages and Incarceration Rates
As discussed in section 2 and shown in section 3, a major use of prison labor was for public
works and construction and maintenance of the railroad, which was essential for the transport
of cash crops for export. Railroad construction began in 1898, and had expanded to its full
extent across the country by the 1950s, as shown in Figure 5. As an additional specification
check, we examine the effects of wages on colonial incarceration rates by distance to the
railroad. Although we do not have data on unemployment rates, the wage time series measure
interacted with distance from each prison to the railroad gives us a proxy for labor market
tightness. We can then test if a tighter labor market intensifies the demand for prison labor,
as reflected in colonial incarceration rates around the railroad. Table 7 reports the estimates
for the effects of rising wages and distance to railroad on short-term incarceration rates at
each prison. While short-term incarceration rates are higher in prisons closer to the railroad
on average, rising wages also increase short-term imprisonment in prisons farther away from
the railroad as reflected in the positive interaction in column (2).
The interpretation of the result is intuitive. While short-term prisoners near the rail-
road are generally used as a reserve of unpaid labor for railroad construction and main-
tenance, increasing wages intensify the demand for unpaid prison labor and worsen labor
shortages and labor market tightness. To increase the share of prison labor, colonial officials
would need to increase the share of prisoners in prisons farther away from the railroad as well.
They could then transport them within the province to conduct work on the railroad and
associated public works as needed (Foreign and Office, 1960). In Appendix A.2, we present
qualitative historical evidence from the archival material supporting this interpretation34 .
34Table A5 in Appendix A.5 shows similar results when we use agricultural commodity price shocks to
examine the effects of crop export price increases on incarceration rates.
34
5 Colonial Imprisonment and Contemporary Trust in Legal Insti-
tutions
To understand the implications of the colonial use of prison labor for present-day views of
state judicial legitimacy, we present a brief discussion and suggestive evidence of the long-run
effects of colonial incarceration on contemporary trust in legal institutions. Given that the
origins of the modern prison and accompanying legal system in Nigeria and other former
British colonies are rooted in the use of state policy around labor coercion, what are the
long-term effects, if any, of exposure to these systems on citizens’ trust in these institutions
today? We use Afrobarometer data from Nigeria on trust in historical legal institutions (e.g.,
police, courts, and tax administration) and trust in individuals (e.g., neighbors, relatives, and
elected local governing council members) to test whether past exposure to coercive, ostensibly
economically influenced colonial prison structures affects trust in legal institutions today.
To test the hypothesis that historical exposure to colonial imprisonment centered
around prison labor may be associated with lowered contemporary trust in legal institu-
tions, with no effect on interpersonal trust, we estimate equations of the following form:
Trustaig st =βPrisonersi+X0
aigstθ+X0
gφ+µs+δt+aigst (5)
where Trustasit is the contemporary trust outcome of interest for individual aresiding
in historical colonial province i, in current sub-district or local government area (LGA) g, in
state sfor the Afrobarometer survey administered in year t. We include vectors of individual
level covariates X0
aigst and LGA-level covariates X0
g
35. All regressions include state and year
fixed effects. Standard errors are clustered at the district (colonial province or current state)
35Data is described in detail in Appendix A.6.
35
level and wild cluster bootstrap p-values are included to account for potentially low numbers
of clusters as before.
We measure Prisonersior long-term colonial imprisonment with the average of long-
term colonial imprisonment over 1920 to 1938 for each province. The rationale here is that,
although there is a significant, high positive correlation between short-term and long-term
colonial imprisonment (.61, p < .001), when it comes to the long-term effects of colonial
prison-labor systems, what stands out in public memory is the stock (long-term imprison-
ment) not the flow (short-term imprisonment) of incarceration rates. And while there is little
recorded information on the determinants of long versus short-term sentences, the historical
literature has documented that crimes against Europeans and colonial officials were often
punished and sentenced more harshly (Abiodun, 2017; Killingray, 1999; Bernault, 2007).
A higher share of long-term imprisonment consisted of relatively more political prison-
ers, pr prisoners that have committed crimes against European colonists (Abiodun, 2017).
One hypothesis is that such long-term imprisonment coupled with the existing economi-
cally motivated system of convict labor is highlighted in local memory as unjust. Exposure
to long-term colonial imprisonment then reduces residents’ trust in legal institutions with
colonial origins such as modern courts, the police, and systems of tax administration, as
a result of repeated negative experiences and long local memories as described in previous
literature (Nunn and Wantchekon, 2011; Lowes and Montero, 2020a,b). A key assumption
here is that there are relatively low levels of internal migration, with most people residing
in their provincial homelands. Although there are no available data on migration, research
has documented significant positive correlations (0.7, p < 0.001) between historic (c.1850)
ethnic/province-level residence and contemporary Afrobarometer respondent locations by
ethnicity (Archibong, 2019; Nunn and Wantchekon, 2011); this suggests that the low migra-
tion assumption is reasonable here.
36
As a falsification test, we examine the effects of long-term colonial imprisonment on
interpersonal trust, and hypothesize that the effects of colonial imprisonment should only
be significant for trust in legal institutions, largely created during the colonial era, but
not interpersonal trust, which perhaps may be determined by factors before the advent
of colonialism, such as the slave trade (Nunn and Wantchekon, 2011). As an additional
falsification test, we examine the relationship between postcolonial imprisonment and trust
outcomes, to check that the result on the negative effect of historical imprisonment on trust in
legal institutions only holds for colonial imprisonment, but not for postcolonial imprisonment,
where prison labor was not used coercively by the state. As a final falsification test, to ensure
that the associations are not being driven by differences in crime between high and low
colonial imprisonment areas, we also test the following “crime propensity” outcomes from
the Afrobarometer: whether the respondent has feared being the victim of a crime in their
home, and how often an individual had to bribe a government official to obtain a document
or permit in the last year.
While Equation 5 includes a rich set of controls, βdoes not identify the causal effect
of long-term colonial imprisonment on trust in legal institutions. It is possible that there
exists an omitted variable, such as lower inherent trust among imprisoned populations, which
determines both long-term colonial imprisonment exposure and trust in legal institutions. To
address this issue, we present results using an instrumental variables approach. We construct
an instrument for our colonial imprisonment outcome that is the interaction between two
variables: (1) the soil suitability for palm oil and (2) an indicator that equals 1 if the colonial
province produced palm oil. The instrument is based on the findings of the strong predictive
power of palm oil production and prices for colonial imprisonment in section 4.4.3. For
instrument validity and for the exclusion restriction to hold, the soil suitability for palm oil
instrument must only affect the trust outcomes through colonial imprisonment.
37
To address concerns that the instrument may directly affect our trust in legal institu-
tions outcomes through a channel other than colonial imprisonment, we include a rich set of
controls alongside the qualitative evidence from the historical literature. The quantitative
results and falsification tests, when coupled with historical accounts of Nigerian residents’
contentions about the injustices of the colonial penal system, are suggestive of the nega-
tive long-term effects of colonial imprisonment on trust in legal institutions like police. We
present further evidence from the qualitative history in Appendix A.6.
Columns (1) to (3) in Table 8 show the OLS results on the association between long-
term colonial imprisonment and trust in historical legal institution outcomes, while columns
(4) to (6) show the results on the association with interpersonal trust outcomes. High levels
of historic long-term colonial imprisonment are significantly, negatively correlated with trust
in legal institutions, with no significant effect for interpersonal trust. The result does not
hold for the relationship between postcolonial imprisonment and trust in legal institutions
outcomes, as shown in Table A7 in the appendix.
Panel A of Table 9 presents the first-stage estimates for the instrument using the “soil
suitability for palm oil x colonial palm oil production” indicator to predict our colonial
imprisonment outcome. The instrument predicts long-term colonial imprisonment, with an
F-stat greater than 10 across all specifications. Panel B of Table 9 reports the second-
stage estimates for our main measure of trust in legal institutions- trust in police- and
one measure of interpersonal trust- trust in relatives. The IV estimates support the OLS
results for some trust outcomes36. Exposure to long-term colonial imprisonment significantly
decreased contemporary trust in police. There is no effect on trust in relatives.
To check that the result on the negative association between colonial imprisonment and
trust in legal institutions is not being driven by underlying differences in crime rates between
36Tables for other trust outcomes are available in Appendix A.6.
38
regions of high versus low levels of colonial imprisonment, we present the results on crime in
Table A8. There is no significant association between colonial imprisonment and our three
crime variables, as shown in columns (1) to (3). Respondents from areas with high levels
of colonial imprisonment are not more likely to experience or commit crimes. Interestingly,
when we examine the links between postcolonial imprisonment and crime, there is a small
significant positive association with the likelihood of an individual bribing a government
official to obtain a document or permit in column (4). The results provide strong, suggestive
evidence of the detrimental long-run effects of colonial incarceration, centered around prison
labor, on contemporary trust in legal institutions like police37 .
6 Conclusion
What are the effects on incarceration when prisoners are viewed and used as a source of labor
to serve economic interests? And what are the potential implications for citizens’ views of
state legitimacy, when an institution of state justice, like prison, is used to serve economic
interests? To answer these questions, we first digitized annual data from archival sources
for British colonial Nigeria. First, we show that prisons were economically valuable to the
colonial regime. We present the first quantitative estimates on the value of prison labor in
British colonial Africa, and find that the value of prison labor is strictly positive over the
colonial period. Even after accounting for an extensive set of prisoner maintenance costs,
the net value of prison labor is strictly positive in the majority of years in colonial Nigeria.
Prison labor constituted a significant share of public works expenditures, up to 249% and
42%, using our gross and net values of prison labor respectively.
We examine the effects of shocks to economic productivity on incarceration and the use
of prison labor. We find that incarceration rates during the colonial period are procyclical.
37A detailed discussion of the channels through which these effects may persist is beyond the scope of this
paper, though we present some preliminary analysis in Appendix A.6.
39
Moderate positive rainfall shocks and positive export price shocks that proxy increased agri-
cultural productivity increase incarceration rates and the use of prison labor in the colonial
period. We provide quantitative and qualitative evidence that to show that a primary reason
for the procyclical behavior of incarceration rates during the colonial period was increased
labor demand for construction and maintenance of public works like railroads, needed to
intensify exports of agricultural commodities during periods of positive productivity shocks.
Labor shortages and tight labor markets increased the demand for unpaid prison labor, re-
flected in the rise in incarceration rates. The effect is reversed in the postcolonial period,
where prison labor is not a major feature of state policy and public finance, and thus negative
shocks increase incarceration rates.
We explore the implications of exposure to prison labor systems for present-day views of
state judicial legitimacy and provide suggestive evidence of the negative long-term effects of
colonial incarceration on contemporary trust in legal institutions. We document a significant
reduction in contemporary trust in legal institutions like police in areas with high historical
levels of colonial imprisonment. The reduction in contemporary trust is specific to legal
institutions, with no effect on interpersonal trust. Historic exposure to judicial systems like
prisons prioritizing economic interests over “justice” may lower individuals’ views of state
legitimacy and trust in legal institutions today. Conversely, the effect does not hold for
exposure to postcolonial imprisonment. Given the renewed debates on the use of prison
labor and the judicial system globally and especially in countries like the US and China,
our paper is the first, to our knowledge, to provide quantitative estimates on the effects on
incarceration when prisoners are used as a store of labor, and its potentially detrimental
effects on citizens’ views of state legitimacy.
40
Figure 1: Top 40 countries/territories for incarceration rates, 2018 with Nigeria incarceration
rates in red (year 1940) and blue (year 2018). Source: World Prison Brief
41
0.2
0.4
0.6
1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940
Year
Share of total convictions
crime_convictions
miscellaneous minor offences
offences against property
offences against revenue, road, social economy colony laws
offences against the person
Share of total convictions by crime, 1920−1940
0.0
0.2
0.4
0.6
1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Year
Share of prison admissions
prison_admissions
miscellaneous minor offences
offences against property
offences against revenue, social economy laws
offences against the person
Share of total prison admissions by crime, 1977−1993
Figure 2: Share of total convictions in colonial courts and share of total prison admissions
in postcolonial period by crime in Nigeria, 1920-1993. Source: see text
Figure 3: Composition of tax revenue in Nigeria, 1930-1980
42
Figure 4: Example of archival data on prisons and wages from the British Blue Books (1922)
Figure 5: Nigeria provinces with colonial prison locations and railroad network shown (left)
and regions (right)
43
Figure 6: Wages, prisoner costs and daily average number in prisons in colonial Nigeria,
1920-1959
Figure 7: Relative value of prison labor, 1920-1959
44
0
20
40
60
1919 1920 1921 1922 1923 1924 1925
Year
Value of wages (pence)
sector
market
prison
Value of wages for bricklayers
0
20
40
1919 1920 1921 1922 1923 1924 1925
Year
Value of wages (pence)
sector
market
prison
Value of wages for carpenters
0
5
10
15
20
25
1919 1920 1921 1922 1923 1924 1925
Year
Value of wages (pence)
sector
market
prison
Value of wages for laborers
0.60
0.65
0.70
0.75
0.80
1919 1920 1921 1922 1923 1924 1925
Year
Fraction below market rate
professions
bricklayer
carpenter
laborer
Percentage of prison wages below market rate
Figure 8: Value of wages for different skill categories in prison and market sectors, 1919-1925
45
100
200
300
1920 1930 1940 1950 1960 1970 1980 1990
Year
Prisoners ( 105)
Mean Nos. of Prisoners (per 10^5 pop.), 1920−1995, Nigeria
Figure 9: Mean number of prisoners per 100,000 population, 1920-1995
500000
750000
1000000
1250000
1500000
0e+00 4e+05 8e+05
Longitude
Latitude
0
200
400
600
prisoners
Prisoners per 100,000 pop., 1920
4
6
8
10
12
14
5 10 15
Longitude
Latitude
50
100
150
200
prisoners
Prisoners per 100,000 pop., 1980
Figure 10: Prison populations in colonial (1920) and postcolonial (1980) Nigeria
46
Table 1: Summary Statistics: Economic shocks and incarceration rates
Statistic N Mean St. Dev. Min Max
Prisoners, 1920-1938
All Prisoners Total 324 1,811.76 2,286.76 3.00 10,231.00
Penal Imprisonment Total 324 1,251.83 1,626.78 2.00 7,010.00
Custody Total 324 509.59 635.57 0.00 3,039.00
Short-Term (<=6 Months) Total 324 1, 051.05 1,409.20 2.00 6,377.00
Medium-Term (6Mo-2Y) Total 324 127.15 171.34 0.00 882.00
Long-Term (>=2yr) Total 324 68.93 84.10 0.00 417.00
1 Previous Total 324 285.26 503.19 0.00 2,967.00
2 Previous Total 324 49.51 73.51 0.00 503.00
3 Previous Total 324 31.80 48.07 0.00 321.00
All Prisoners /100,000 324 240.73 254.56 0.26 1,123.30
Penal Imprisonment /100,000 324 162.03 169.55 0.26 759.99
Custody /100, 000 324 71.73 83.47 0.00 333.66
Short-Term /100,000 324 134.66 144.95 0.16 649.43
Medium-Term /100,000 324 16.56 18.26 0.00 80.45
Long-Term /100,000 324 10.18 12.88 0.00 83.45
Share w/ 1 Previous 324 0.11 0.15 0.00 0.90
Share w/ 2 Previous 324 0.02 0.03 0.00 0.32
Share w/ 3 Previous 324 0.02 0.03 0.00 0.18
Agricultural Commodities and Rainfall Deviation, 1920-1938
Cocoa Producing 393 0.15 0.35 0.00 1.00
Groundnut Producing 393 0.18 0.39 0.00 1.00
Palm Oil Producing 393 0.19 0.39 0.00 1.00
Log Cocoa Price 393 1.04 0.40 0.47 1.96
Log Groundnut Price 393 0.35 0.36 0.36 0.88
Log Palm Oil Price 393 0.72 0.53 0.22 1.69
Rainfall Dev. 393 0.00 0.97 2.21 4.08
Rainfall Dev. Sq. 393 0.95 1.83 0.00 16.67
Positive Rainfall Shock (M) 393 0.17 0.38 0.00 1.00
Negative Rainfall Shock (E) 393 0.30 0.46 0.00 1.00
Positive Rainfall Shock (E) 393 0.21 0.41 0.00 1.00
Prisoners and Rainfall Deviation, 1971-1995
All Prisoners Total 871 2,005.81 1,210.56 104.00 7, 092.00
All Prisoners /100,000 871 92.48 60.43 9.91 361.99
Share w/ 1 Previous* 6 0.21 0.02 0.18 0.23
Share w/ 2 Previous* 6 0.12 0.02 0.10 0.16
Share w/ 3 Previous* 6 0.13 0.04 0.05 0.18
Rainfall Dev. 560 0.01 0.30 0.62 1.06
Rainfall Dev. Sq. 560 0.09 0.12 0.00 1.11
Positive Rainfall Shock (M) 560 0.49 0.50 0.00 1.00
Negative Rainfall Shock (E) 560 0.04 0.19 0.00 1.00
Positive Rainfall Shock (E) 560 0.01 0.11 0.00 1.00
Notes: See text and online appendix for details. *denotes that data is based on available time series information from
1975-1980.
47
Figure 11: Prisoners and agricultural commodity prices, 1920-1995, Nigeria
Figure 12: Agricultural commodity production in colonial Nigeria
48
Table 7: Effect of wages and distance to railroad on colonial incarceration rates
Short-Term Long-Term
(1) (2) (3) (4)
Distance to railroad 0.3011.479∗∗ 0.018 0.029
(0.158) (0.681) (0.023) (0.099)
[0.005] [0.010] [0.440] [0.807]
Distance x Log wages 0.401∗∗ 0.004
(0.191) (0.033)
[0.038] [0.927]
Mean of outcome 46.198 46.198 3.990 3.990
District FE Yes Yes Yes Yes
Year FE Yes Yes Yes Yes
Observations 938 938 822 822
Clusters 21 21 21 21
Notes: Regressions estimated by OLS. Robust standard errors in parentheses clustered by district, where district
is colonial province for colonial data. Wild cluster bootstrap (by district) p-values are in brackets. Observations
are individual prisons. Dependent variables in (1)-(4) are prisoners in each prison per 100,000 population of the
province broken down by short-term (less than 6 months) sentence and long-term (greater than 2 years) sentence
over 1920-1938. Covariates are distance to railroad in km and log urban unskilled wages. District FE are colonial
province fixed effects in (1)-(4). ∗∗∗Significant at the 1 percent level, ∗∗ Significant at the 5 percent level, Significant
at the 10 percent level based on clustered standard errors in parentheses.
54
Table 9: First and second-stage estimates for interacted instrument and effect of colonial
imprisonment on trust in police (legal) and trust in relatives (interpersonal)
Panel B: Second-Stage 2SLS Estimates
Trust in Police Trust in Relatives
(1) (2) (3) (4)
Prisoners per 100,000 pop. 0.021∗∗∗ 0.022∗∗∗ 0.016 0.005
(0.005) (0.005) (0.024) (0.035)
Panel A: First-Stage Estimates
Soil Suitability for Palm Oil
x Colonial Palm Oil Production 0.191∗∗∗ 0.187∗∗∗ 0.214∗∗∗ 0.227∗∗∗
(0.050) (0.040) (0.053) (0.045)
F-Stat of Excluded Instrument 14.80 21.65 16.13 25.21
Population Density Yes Yes Yes Yes
Individual Controls Yes Yes Yes Yes
Geographic Controls No Yes No Yes
Disease Controls No Yes No Yes
Precolonial and Colonial Controls No Yes No Yes
District FE Yes Yes Yes Yes
Year FE Yes Yes Yes Yes
Observations 10,693 8,349 4,355 3,415
Clusters 21 21 21 21
Notes: Regressions estimated by OLS. Robust standard errors in parentheses clustered by colonial province. The unit of
observation is an individual. Prisoners per 100,000 pop. are averages of long-term (>2 years sentence) prisoners per 100,000
population (1939 pop.) over 1920 to 1938. Trust variables are from the Afrobarometer samples over 2003 to 2014 and
as defined in the main text. Trust outcomes are reported trust levels on a scale of 0-3, where “Not at all”= “0”, “Just a
little”=“1”, “Somewhat”=“2”, “A lot”=“3”. All regressions use district fixed effects at the current state level in Nigeria,
year fixed effects, educational attainment fixed effects and controls for sub-district or local government area population
density in 2006. Individual controls include age, age squared and gender. Geographic controls at the sub-district level
include ruggedness, indicators for petroleum, seacoast and mean elevation in alternate specifications. Disease controls at
the sub-district level include malaria suitability and tse tse fly suitability in alternate specifications with results unchanged.
Precolonial and colonial controls at the ethnicity-level include the level of precolonial centralization and total exports of
slaves from the region during the Atlantic slave trade. ∗∗∗Significant at the 1 percent level, ∗∗Significant at the 5 percent
level, Significant at the 10 percent level.
56
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A Appendix (For Online Publication)
Contents
1 Introduction 2
2 Prison Labor in Colonial Africa 8
2.1 AHistoryofForcedLabor ............................ 8
2.2 Prison Labor in British Colonial Nigeria . . . . . . . . . . . . . . . . . . . . 10
3 Estimating the Value of Prison Labor 15
3.1 HistoricalData .................................. 15
3.2 EmpiricalStrategy ................................ 16
3.3 Value of Prison Labor Results . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.3.1 Comparing Imputed Estimates of the Value of Prison Labor to Re-
ported Colonial Estimates . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Effects of Economic Shocks on Incarceration Rates and the Use of Prison
Labor 21
4.1 Data on Incarceration Rates and Economic Shocks . . . . . . . . . . . . . . 21
4.2 SummaryStatistics................................ 23
4.3 EstimatingEquations............................... 24
4.3.1 Nonlinear Effects of Economic Shocks on Incarceration Rates . . . . . 25
4.3.2 Identifying the Effects of Positive Rainfall Shocks on Incarceration Rates 27
4.3.3 Effects of Cash Crop Price Shocks on Colonial Incarceration Rates . . 28
4.4 Results....................................... 29
4.4.1 Nonlinear Effects of Economic Shocks on Incarceration Rates Results 29
67
4.4.2 Identifying the Effects of Positive Rainfall Shocks on Incarceration
RatesResults ............................... 31
4.4.3 Effects of Cash Crop Price Shocks on Colonial Incarceration Rates
Results................................... 33
4.4.4 Railroad, Wages and Incarceration Rates . . . . . . . . . . . . . . . . 34
5 Colonial Imprisonment and Contemporary Trust in Legal Institutions 35
6 Conclusion 39
A Appendix (For Online Publication) 67
A.1 Data and Archival Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
A.2 A Further History of Forced and Prison Labor in Colonial Africa . . . . . . . 72
A.3 North-South Differences in the Distribution of Colonial versus Native Prisons 77
A.4 Value of Prison Labor Specification Checks . . . . . . . . . . . . . . . . . . . 80
A.4.1 Value of Prison Labor: Adjusting for Inflation . . . . . . . . . . . . . 80
A.4.2 Value of Prison Labor: Measuring Bias in Estimates . . . . . . . . . . 83
A.4.3 Relative Value of Prison Labor: Comparison to Recurrent Maintenance
Public Works Expenditure . . . . . . . . . . . . . . . . . . . . . . . . 84
A.5 Suggestive Evidence of Sentence-Switching in Response to Short-Term Eco-
nomic Shocks: Custody and Short-Term Incarceration Rates and Further Ro-
bustness ...................................... 85
A.6 Relationship between Colonial Imprisonment and Trust in Colonial Institu-
tions versus Interpersonal trust . . . . . . . . . . . . . . . . . . . . . . . . . 88
68
List of Figures
1 Top 40 countries/territories for incarceration rates, 2018 with Nigeria incar-
ceration rates in red (year 1940) and blue (year 2018). Source: World Prison
Brief ........................................ 41
2 Share of total convictions in colonial courts and share of total prison admis-
sions in postcolonial period by crime in Nigeria, 1920-1993. Source: see text 42
3 Composition of tax revenue in Nigeria, 1930-1980 . . . . . . . . . . . . . . . 42
4 Example of archival data on prisons and wages from the British Blue Books
(1922) ....................................... 43
5 Nigeria provinces with colonial prison locations and railroad network shown
(left)andregions(right) ............................. 43
6 Wages, prisoner costs and daily average number in prisons in colonial Nigeria,
1920-1959 ..................................... 44
7 Relative value of prison labor, 1920-1959 . . . . . . . . . . . . . . . . . . . . 44
8 Value of wages for different skill categories in prison and market sectors, 1919-
1925 ........................................ 45
9 Mean number of prisoners per 100,000 population, 1920-1995 . . . . . . . . . 46
10 Prison populations in colonial (1920) and postcolonial (1980) Nigeria . . . . 46
11 Prisoners and agricultural commodity prices, 1920-1995, Nigeria . . . . . . . 48
12 Agricultural commodity production in colonial Nigeria . . . . . . . . . . . . 48
A1 Breakdown of estimated public works expenditure, Northern (NP) and South-
ern (SP) Provinces, 1920 and 1935 . . . . . . . . . . . . . . . . . . . . . . . 76
A2 Native administration prisons, 1940 . . . . . . . . . . . . . . . . . . . . . . . 78
A3 Native prison incarceration rates, 1940 and 1945 . . . . . . . . . . . . . . . . 79
A4 Value of prison labor, real vs nominal estimates . . . . . . . . . . . . . . . . 80
69
A5 Alternate prison and value of labor coercion measures, 1920-1938 . . . . . . 84
A6 Relative value of prison labor, 1920-1959 . . . . . . . . . . . . . . . . . . . . 85
List of Tables
1 Summary Statistics: Economic shocks and incarceration rates . . . . . . . . 47
2 Rainfall shocks and colonial (1920-1938) and postcolonial (1971-1995) incar-
cerationrates ................................... 49
3 Rainfall shocks and colonial (1920-1938) and postcolonial (1971-1995) incar-
cerationratesbyregion.............................. 50
4 Rainfall shocks (by type) and colonial (1920-1938) and postcolonial (1971-
1995) incarceration rates breakdown . . . . . . . . . . . . . . . . . . . . . . . 51
5 Rainfall shocks and colonial (1920-1938) and postcolonial (1971-1995) incar-
cerationratesbyregion.............................. 52
6 Agricultural commodity prices and colonial incarceration rates . . . . . . . . 53
7 Effect of wages and distance to railroad on colonial incarceration rates . . . . 54
8 OLS Estimates: Relationship between colonial imprisonment and present-day
trust in historical legal Institutions versus interpersonal trust . . . . . . . . . 55
9 First and second-stage estimates for interacted instrument and effect of colo-
nial imprisonment on trust in police (legal) and trust in relatives (interpersonal) 56
A1 Relationship between precolonial centralization and number of colonial vs na-
tiveprisons .................................... 79
A2 Value of prison labor, 1920-1959 . . . . . . . . . . . . . . . . . . . . . . . . . 81
A3 Value of prison labor, real estimates . . . . . . . . . . . . . . . . . . . . . . . 82
A4 Rainfall shocks (by type) and colonial (1920-1938) incarceration rates by cus-
tody/awaiting trial category . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
70
A5 Effect of agricultural commodity prices and distance to railroad on colonial
incarcerationrates ................................ 87
A6 Summary Statistics: Afrobarometer Results . . . . . . . . . . . . . . . . . . 91
A7 Falsification Test: OLS Estimates of relationship between postcolonial impris-
onment and present-day trust in historical legal Institutions versus interper-
sonaltrust..................................... 92
A8 OLS Estimates: Relationship between colonial and postcolonial imprisonment
and present-day crime outcomes . . . . . . . . . . . . . . . . . . . . . . . . . 93
A9 IV Estimates: Effect of relationship between colonial imprisonment and present-
day trust in historical legal Institutions versus interpersonal trust . . . . . . 94
A10 OLS Estimates: Colonial palm oil suitability and production instrument does
not predict postcolonial imprisonment . . . . . . . . . . . . . . . . . . . . . . 95
A.1 Data and Archival Materials
Primary data from British Online Archives, Nigeria [Colony and Protectorate] Blue
Book, 1914-1940. British Foreign and Commonwealth Office
Nigeria, Annual Report on the Prisons Department, Northern and Southern Provinces,
1914-1960
NAI, CSO 26/2 09591 Vol.1 ‘Lieutenant Governor Southern Province to Resident Cal-
abar Province: Memorandum on Prison labor’ 23rd April 1923
Annual Report on the Treatment of Offenders, 1947, Nigeria
Nigeria Annual Abstract of Statistics, 1975-1997
71
A.2 A Further History of Forced and Prison Labor in Colonial Africa
Prison labor was a small part of a larger regime of domestic forced labor in colonial Africa.
A small but rich and growing labor history of colonial Africa has documented the ways in
which the so-called “revenue imperative” of colonial governments, whose objectives were to
maximize revenue extraction while minimizing costs of administration in Africa, led to the
establishment of coercive labor contracts in the region (Freund, 1984; Maul, 2007; Okia, 2012;
Gardner, 2012; Cooper, 1996; Harris, 1914; Trevor, 1936; van Waijenburg, 2018; Alexopoulou
and Juif, 2017). Following the signing of the Final Act of Congress of Vienna in 1815
to abolish slavery, a series of contentious debates about the nature of forced labor, and
particularly the extent to which forced labor could be employed to fulfill the revenue demands
in Europe’s African colonies continued through the middle of the 20th century (Maul, 2007).
The debates highlighted a number of responses to Europe’s so-called “Africa labor question”,
where, faced with the realities of labor scarcity, increased demand for labor from both private
and public sector employers and an indigenous labor force with their own preferences for
work, the discussions shifted from questions about how to institute European systems of
wage labor and private property ownership in the colonies to the amount of coercion a
“civilized government” could use (Cooper, 1996).
Faced with these options - low pay for often dangerous, back-breaking work on railroads
or in mines, under sometimes racist38, difficult employers - many Africans preferred self-
employment in subsistence farming to working in the colonial wage labor market (Frankema
and Van Waijenburg, 2012; Harris, 1914). To address these constraints, colonial governments
enacted a series of strategies to meet labor and revenue demands. Among these strategies
38Harris (1914) reports of the comments of a white employer, Mr E Tarlton in Kenya who, in complaining
about labor shortages he faced, told the 1912 labor Commission in the East Africa Protectorate that “this
is my busiest season and my work is entirely upset, and it is hardly surprising if I am in a red-hot state
bordering on a desire to murder everyone with a black skin who comes within sight”, p. 821.
72
included the use of direct taxation like hut and poll taxes requiring cash payment to press
Africans into the wage labor market, the use of labor tax legislation to force Africans to
donate a certain number of hours of often unpaid labor to private and public sector work,
and the use of precolonial communal labor requirements to compel Africans, under the
direction of the chiefs, to provide unpaid labor for private and public works projects (Okia,
2012; Harris, 1914; Trevor, 1936; van Waijenburg, 2018; Cooper, 1996).
In colonial Nigeria, forced labor regulation included the Native House Rule Ordinance
of 1901 and the Roads and Creek Proclamation of 1903, both of which mandated labor for
‘public purposes’ for all men between 15 and 50 years old and all women between 15 and
45 years old (Ofonagoro, 1982). The Masters and Servants Proclamations of 1901 and 1903
also instituted forced labor in colonial Nigeria, granting Native Administrators or chiefs the
authority to coerce local laborers for up to 24 working days in a year or 1 out of 12 months.
Laborers were frequently employed on public works projects and physically intensive manual
tasks like porterage, carrying pounds of baggage for British officials through often dangerous
environments like military expeditions for “miserable” below market-wage pay (Ofonagoro,
1982; Okia, 2012).
Following a series of forced labor scandals, one of which was the sanctioning of tor-
ture, mutilation and murder of millions of Congolese for the rubber extraction trade under
Belgium’s King Leopold through the 1890s, another debate on the labor question led to
the passing of the Slavery Convention by the League of Nations in 1926 (Hochschild, 1999;
Lowes and Montero, 2020a). The Convention urged European powers to abolish slavery “in
all its forms” and the League requested that the International Labor Organization (ILO)
investigate the “best means of preventing forced or compulsory labor from developing into
conditions analogous to slavery” (Cooper, 1996). p. 29. These exchanges led to the passing
of the Forced Labor Convention at the 1930 ILO conference which forbade the use of forced
73
labor for private industry where forced labor was defined as “all work or service which is ex-
tracted from any person under the menace of any penalty and for which the said person has
not offered himself voluntarily” (Cooper, 1996). p. 2939. The Convention made exceptions
for the use of forced labor for public works, ‘penal and communal labor in the public sector
and compulsory military service’ (Kunkel, 2018; Killingray, 1989).
While Britain was the first to sign the ILO article, followed by France and a few other
European governments in the mid 20th century, it, and its colonial peers continued, and in
some cases intensified forced labor practices through the use of ‘unofficial’ communal labor
for public works projects (Kunkel, 2018). The practice is exemplified in a 1944 statement
made by the then district commissioner of Northern Ghana’s Builsa district, who, in showing
the chief commissioner of the Northern territories the new projects the colonial government
had started funding in the region over the past years, among which were schools, rural
roads, bridges and dams, argued for the financial viability of the district by informing the
commissioner that the chief had supplied the government with unpaid communal labor:
“nearly all the labourers I find whom your Honour saw working in the new Sandema dam
are ‘voluntary’ workers, there are only seven names on the time sheet which is encouraging.
(Wiemers, 2017), p.239. Many of these coercive labor practices continued through the end
of the 1930s and as late as the 1950s in some regions, when African workers began to
actively organize labor unions and strikes to protest labor contracts with fixed low wages
amidst rising food prices in the mid to late part of the 1930s after the Depression (Cooper,
1996). Among the most famous strikes were the 1935 Copperbelt strike of African miners in
Northern Rhodesia, the Mombasa general strike, the Dar es Salam dock strike and a number
of strikes on the railways of the Gold Coast in 1939 (Cooper, 1996).
In Nigeria, although prisoners were most often employed on public works, public works
39ILO 29, Article 2 s 2a, c, e, Articles 4 and 5
74
expenditure was a small fraction of overall colonial expenditures between 1920 and 1940,
composing an average of 2.8% of colonial expenditures over the period40. As of 1920, 30%
of expenditure was on railways, 12% on servicing public debt, and 19% of expenditure was
devoted to defense spending on ‘marine, political and West African Frontier Force’. The
majority of revenues in 1920 were from customs (46%) and railways (23%). By 1936, the
share of expenditure on railways had dropped to 8% of overall expenditure, with public debt,
and pensions and gratuities remaining as the top spending categories for the colonial regime.
Public works expenditure in both years remained low at around 2%. While revenue from the
railway could be used to service railroad expenditure, only 2.8% of colonial expenditures,
on average, was allocated for less costly public works projects, like spending on civil roads,
canals, bridges and “buildings not of a military nature” (e.g. court houses and hospitals). A
breakdown of the top ten, where available, categories for estimated public works expenditure
in 1920 and 1935 for the Northern and Southern provinces is shown in Figure A141. In the
Northern provinces in 1920, roads, public offices, hospitals and court houses accounted for
80% of overall public works expenditure, while government quarters, industrial plants and
roads accounted for 68% of overall public works expenditure in Southern provinces in the
same year. By 1935, the major public works expenditure categories in both the Northern
and Southern provinces were waterworks, electricity infrastructure projects and government
offices with 100% and 95% of overall public works expenditure in Northern and Southern
Provinces respectively. Convict labor, by colonial officials’ own admissions, was an essential
part of funding these public works projects (Foreign and Office, 1960). The use of prison
labor for colonial public works projects continued through the 1950s in British colonial Africa
with an estimated between 1 in 300 and 1 in 500 Africans imprisoned over 1930 through the
40Author’s estimates from Annual Report on Prisons Data over 1920 to 1940.
41We use estimated rather than actual expenditure in a given year to reflect colonial government expecta-
tion around expenditure and to account for unfinished projects and multiple missing entries in the ’spending
to date’ values provided in the Blue Books records.
75
1950s, in contrast with 1 in 2000 British natives in Britain (Hynd, 2015).
Offices and Court Room, Kano
Four European Quarters (Type VII) −Kaduna
Office for Station Magistrate and Court House, Kaduna
Native Hospital, Minna
1 European Quarters (Type II), Jos
European Hospital and Fittings, Kaduna
Jos−Bauchi Road
Joinery and Machine Shops, Kaduna
Public Offices, Kaduna
Zaria Sokoto Road
0.0 0.1 0.2 0.3
Share of total estimated expenditure
Category
Public works estimated expenditure breakdown, NP 1920
Butchers’ Stalls − Zaria Township
Landing Ground − Maiduguri
Electricity Scheme − Kaduna
Landing Ground, Kaduna
Landing Ground − Minna
Quaters and Offices, New Protectorate Court
Landing Ground − Kano
Waterworks Scheme − Okene
0.0 0.2 0.4 0.6
Share of total estimated expenditure
Category
Public works estimated expenditure breakdown, NP 1935
Akure Ondo Road
Completion of Agege−Lafenwa Road
Igbara−Oke−Igbara−Odo−Ikere Road
Enugu−Abakaliki Road
Produce Wharves, Lagos
Customs Shed "I", Lagos
Four Quarters, Type IV, Port Harcour t
Four Quarters, Type IV, Benin
Brick and Tile Plant, Ishiago
Ten Quarters, Type IV of 1920, Lagos
0.00 0.05 0.10 0.15
Share of total estimated expenditure
Category
Public works estimated expenditure breakdown, SP 1920
Electricity Supply Works − Enugu
Workshop and Lecture Hall, Higher College, Yaba
Mamfe − Bamenda Road
Waterworks Scheme − Calabar
Waterworks Schemes − Ife
Waterworks Scheme − Abeokuta
Waterworks Scheme − Benin City
Electricty Scheme − Abeokuta
Electricity Supply Works − Lagos
Tank & Non−tank Latrines, Lagos
0.00 0.05 0.10 0.15 0.20
Share of total estimated expenditure
Category
Public works estimated expenditure breakdown, SP 1935
Figure A1: Breakdown of estimated public works expenditure, Northern (NP) and Southern
(SP) Provinces, 1920 and 1935
76
A.3 North-South Differences in the Distribution of Colonial versus Native Pris-
ons
There was a dual system of prison administration in Nigeria, under the Native Adminis-
tration, overseen by local chiefs under indirect rule. Under indirect rule, areas with more
centralized precolonial institutions were granted more autonomy to oversee local adminis-
tration, including on the creation and administering of Native Authority prisons. Results
from Table A1 confirm a significant positive correlation between the level of precolonial cen-
tralization and the numbers of native prisons (Archibong, 2019). Although we don’t have
detailed Native Administration prisons data over the 1920 to 1938 period, Figure A2 shows
the distribution of Native Administration prisons in 1940, for the first year of available data
in the colonial archives.
Native Authority or Administration prisons were more heavily concentrated in the
Northern provinces, which had a more extensive history of organized precolonial institutions
around courts than their southern counterparts (Killingray, 1999). Precolonial political in-
stitutions are proxied using Murdock’s (1967) “Jurisdictional Hierarchy Beyond the Local
Community Level” called the precolonial centralization index here. The precolonial central-
ization index or “Jurisdictional Hierarchy Beyond the Local Community Level” variable is an
index of “political complexity” that assigns a score between 0 to 4 to each ethnic region unit
and describes the number of political jurisdictional hierarchies above the local community
level for each unit. The score is defined as follows: 0 represents so-called “stateless soci-
eties”,“lacking any form of political organization”, 1 and 2 are petty and larger paramount
chiefdoms, 3 and 4 are large, more organized states. Table A1 provides suggestive evidence
of the positive correlation between precolonial centralization and the number of native pris-
ons in a colonial province. While prison labor was a feature of all colonial era prisons, both
Native Administration and colonial government prisons, since Native Authority prisons were
77
more numerous than colonial prisons42, Native Authority prisons processed more prisoners
than colonial prisons in the north, with the share of prison labor coming primarily from
Native Authority prisons in the Northern provinces.
Figure A2: Native administration prisons, 1940
42On average there were 18 colonial prisons over 1920 to 1938 in the Northern provinces vs 56 Native
Authority prisons in 1940. The ratio for Southern provinces over those periods was 54 to 9. Source: colonial
archives.
78
Table A1: Relationship between precolonial centralization and number of colonial vs native
prisons
Native prisons Colonial prisons
(1) (2)
Precolonial centralization 0.5990.515
(0.316) (0.339)
Constant 1.447∗∗∗ 2.112∗∗
(0.265) (0.969)
Observations 22 19
R20.124 0.026
Notes: Regressions estimated by OLS. Robust standard errors in parentheses.
Unit of observation is Murdock ethnic region. Precolonial centralization is
Murdock centralization index as defined in text.
∗∗∗Significant at the 1 percent level, ∗∗ Significant at the 5 percent level,
Significant at the 10 percent level.
Figure A3: Native prison incarceration rates, 1940 and 1945
79
A.4 Value of Prison Labor Specification Checks
A.4.1 Value of Prison Labor: Adjusting for Inflation
The measures of values of prison labor used so far have been calculated using nominal values
as shown in Figure A4(a) and Table A2. One potential side effect of using nominal values
when observing trends over time is that is it difficult disentangle the difference between
changes in the observed variable and changes in the price level. To ensure that the trends in
our measure of prison labor are not driven by changes in the price level, we convert the values
into real values using 1920 as the base year, following the technique outlined in Frankema
(2011)43. Figure A4(b) and Table A3 show trends in the value of prison labor, adjusted for
inflation. The trends remain unchanged using real versus nominal estimates of prison labor
and the value of prison labor is not driven by changes in the price level.
Figure A4: Value of prison labor, real vs nominal estimates
43Using Feinstein (1972)’s British price index data.
80
Table A3: Value of prison labor, real estimates
Year Real total value of
prison labor (PL),
estimate
Real net value of
PL- less food costs
Real net value of
PL- less prison
costs
Real