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Socially Embedded
Preferences,
Environmental
Externalities, and
Reproductive Rights
AISHA DASGUPTA
PARTHA DASGUPTA
AMONG ECONOMISTS and demographers, the dominant view of the ef-
fect of growing human numbers on the natural environment has alter-
nated between concern and dismissal. If in the years immediately following
World War II scholars were anxious that population growth would retard
economic development in poor countries, they have not worried in re-
cent decades. A series of inuential reviews of the modern growth expe-
rience (National Research Council 1986; Birdsall 1988; Kelley 1988; Tem-
ple 1999; Helpman 2004) studied cross-country data and saw a negligible
link—possibly even a small positive link—between population growth and
growth in per capita gross domestic product. These analyses were convinc-
ing, but the underlying assumption that economic betterment is best seen
in terms of growth in GDP per capita should be questioned. The presence
of the qualier “gross” in gross domestic product signals that the measure
does not record the depreciation of natural capital that can accompany the
production of goods and services.1Other things equal, depreciation of nat-
ural capital reduces a nation’s productive capacity, the correct measure of
which is an inclusive notion of wealth. And normative economics tells us
that the index we should deploy for assessing the sustainability of human
development is the wealth of nations (Arrow et al. 2012), not the GDP of
nations, nor the Human Development Index of nations.2
A rich demographic literature has offered insights into fertility behav-
ior in the contemporary world. Those insights have been used by the United
Nations to frame family planning programs (UNFPA 1995). More recently
they have inuenced the way family planning has been placed within the
UN’s Sustainable Development Goals. We apply those insights to argue that
the basis on which women’s expressed desired for children is elicited mis-
estimates their desire. More importantly, it underestimates women’s true
need for family planning.
POPULATION AND DEVELOPMENT REVIEW 43(3): 405–441 (SEPTEMBER 2017) 405
406 SOCIALLY EMBEDDED PREFERENCES
Parental desires and wants constitute one set of factors in popula-
tion ethics. Another set of factors is the effect on others of a household’s
reproductive behavior. Ehrlich and Holdren (1971) coined the metaphor
I=PAT to trace humanity’s impact on the biosphere (more generally,
the Earth system) to population size, afuence (income per capita), and
“technology”-in-use (including knowledge, institutions, social capital). The
authors observed that Nature responds to the demands we make of it, not
to rates of change in those demands nor to rates of change in the rates of
change in those demands. Their observation has had little inuence on ei-
ther economics or demography. That the growth rate of global population
has been declining in recent years is seen by development experts as a hope-
ful sign of a transition to sustainable development (World Bank 2016); in
fact the decline does not say much about the prospect of realizing sustain-
able development. Under foreseeable technological developments, a long-
run population of 10–11 billion can be expected to make far greater de-
mands on the biosphere than one of, say, 3 billion. Recent books that have
drawn attention to the remarkable gains in the standard of living during the
past century have focused on advances in scientic knowledge and the accu-
mulation of manufactured and human capital; the state of the biosphere and
its trends accompanying that progress have for the most part gone unnoted
(Micklethwait and Wooldridge 2000; Ridley 2010; Deaton 2013; Lomborg
2014; Norberg 2016). But humanity’s future will be shaped by the portfolio
of assets we choose to hold and the balance we strike between them and
the size of our population. It should be a concern that the enormous eco-
nomic success we have enjoyed in recent decades may be a down payment
for future failure.
Among the visible products of the biosphere are food, bers, fuel, and
fresh water, but many of the services it provides are hidden from view.
Ecosystems maintain a genetic library, preserve and regenerate soil, x ni-
trogen and carbon, recycle nutrients, control oods, mitigate droughts, l-
ter pollutants, assimilate and decompose waste, pollinate crops, operate the
hydrological cycles, and maintain the gaseous composition of the atmo-
sphere. Since most of these services are not visible, they are easy to over-
look. Some environmental stresses are global, many are spatially localized;
some occur slowly and may therefore miss detection until it is too late, while
others are noticeable and a cause of persistent societal stresses. The wide
divergence of environmental problems may explain why people differ in
the perceived urgency that they express about carbon emissions and loss
of biodiversity that extend beyond nations, regions, and continents; about
degradation of oceanic life arising from the energy and materials we release
into them; about the hardship communities face when grasslands transform
into shrub-lands; and about declines in rewood, water sources, and soil
productivity that are specic to the needs and concerns of the poor in vil-
lage communities.3Environmental problems differ in their location and in
AISHA DASGUPTA /PARTHA DASGUPTA 407
their spatial and temporal scales, which is why it is possible to be optimistic
about humanity’s collective ability to overcome environmental problems if
one studies small-scale environmental successes (Balmford and Knowlton
2017) but to be deeply worried if one looks at continued failure to stem
global biodiversity loss. Contemporary data at the global level tell us that
environmental successes to date have been few and far between.
Environmental scientists have compiled data on the state of the bio-
sphere and its changing character over past decades (MEA 2005a–d). Cor-
responding data at local levels are scattered and range from the detailed to
nothing. But global happenings are an aggregate of large numbers of local
happenings. Below we develop an analytical framework for studying fer-
tility behavior and humanity’s impact on the natural environment at local
levels (Part I) and use aggregate data to obtain a quantitative assessment
of the impact at the global level (Part II). We nd that humanity’s demand
for Nature’s goods and services in the aggregate exceeds by a considerable
margin Nature’s ability to supply them. Our hope is that the framework we
construct will point to the way the balance between population size and the
portfolio of our assets could be struck.
Externalities
Processes driving the balance between population size and the assets we
hold give rise to externalities, which are the unaccounted-for consequences
for others of actions taken by one or more persons. The qualier “unac-
counted for” means that the consequences in question follow without prior
engagement with those who are affected.
The way we have formulated the notion of externalities could appear
ineffective, on grounds that our actions inevitably have consequences for
future generations, who by the nature of things cannot engage with us.
In fact future people engage with us constantly, albeit indirectly. Parents
care about their children and know that they in turn will care about their
children. By recursion, thoughtful parents take the well-being of their de-
scendants into account when choosing the rates at which they save for their
children and invest in them. Intergenerational engagement would be im-
perfect if parents choose without adequate concern for their children (e.g.
if they discount the future well-being of their children at overly high rates).
Externalities across the generations would be rampant in that case. We ig-
nore that line of analysis here. Our aim is to study systematic reasons why
choices made even by thoughtful parents do not reect adequate engage-
ment with others’ descendants. Since they are symptoms of institutional fail-
ure, externalities cannot be eliminated without considered and tenacious
collective action. That is why reasoned reproductive decisions at the indi-
vidual level can nevertheless result in collective failure.
408 SOCIALLY EMBEDDED PREFERENCES
Two broad categories of externalities are studied here. One consists
of the consequences of household consumption and reproduction that
work through open-access resources (“the commons”). That is the familiar
variety of externalities, much noted and studied by environmental
economists (e.g. Baumol and Oates 1975). Institutional failures in this class
of externalities arise from an absence of appropriate property rights to Na-
ture’s goods and services. By property rights we mean not only private
rights, but also communitarian and public rights. One reason rights to nat-
ural capital are difcult to dene, let alone enforce, is that Nature is con-
stantly on the move (the wind blows, particulates diffuse, rivers ow, sh
swim, birds and insects y). No one can contain the environmental asset
they damage. As a result, the price paid by someone for environmental ser-
vices (the private cost) is less than the cost borne by all (the social cost). In
cases involving the global environment, such as the atmosphere as a sink
for carbon emissions, the damage an individual suffers from his own emis-
sions is negligible even though the damage to all from the climate change
that arises from everyone’s emissions is large and positive. From the collec-
tive point of view there is excessive use of the atmosphere as a carbon sink.
The environmental externalities to which our use of open-access resources
gives rise are adverse.
The other category of externalities we uncover here has been less
studied in the literature. It arises because our desire to have children is in
part inuenced by the number of children others have. No doubt a single
household cannot much inuence others, but the aggregate effect of all
households on one another is not negligible. The social embeddedness of
household preferences—we call the resulting behavior “conformist”—can
lead to high fertility even when those same preference structures can sustain
the low fertility that perhaps all households would prefer. Either situation—
high fertility (allied to low educational attainment of children) or low fertil-
ity (allied to high educational attainment)—can be self-sustaining. Fertility
transitions can be interpreted as moves from one equilibrium to the other.
The two classes of externalities have very different internal structures.
The problem of choice in the use of open-access resources resembles the
well-known prisoner’s dilemma. In contrast, socially embedded preferences
give rise to coordination games. Communities can turn the latter class of
externalities to their advantage by coordinating behavior (e.g. through an
appeal to social norms), whereas the former requires, at least over the
global commons, more traditional policy measures such as environmental
regulations.
Outline of the essay
In Part I (Sections 1–5) we study the clash of rights among contemporaries
and between present and future people. We then study the implications
AISHA DASGUPTA /PARTHA DASGUPTA 409
of those clashes for the design of family planning programs. In attribut-
ing rights to future people, we are appealing to a widely shared view that
no matter who and how many our descendants happen to be, they will
have a justiable claim to a reasonably abundant resource base. Future peo-
ple’s personal identities do not matter in this context. The question arises
whether the environmental externalities we identify here are quantitatively
signicant. To explore that question, we make use of global estimates of hu-
manity’s demand for the biosphere’s products and services relative to their
supply. That exercise is conducted in Part II (Sections 6–10).
In Section 1 we review the proposed distinction by the legal philoso-
pher Charles Fried between positive and negative rights. We apply the dis-
tinction to study the clash between the moral directives owing from ad-
verse environmental externalities and the exercise of personal rights. That
step acts as a backdrop for Section 2, where we recall that some prominent
social scientists have insisted that there are no environmental externalities
arising from procreation.
In Section 3 we explore the interplay of parental motivations and
socio-ecological constraints that help to explain differences in reproductive
behavior across regions and across socioeconomic groups within regions.
We look briey also at what has been called “African exceptionalism” in
reproductive behavior and identify a class of inter-household externalities
that may have contributed to high fertility rates in that region. Socially
embedded preferences are identied in Section 4 as a source of inter-
household externalities, sustaining high fertility rates. We note possible
mechanisms by which behavior stemming from such preferences can be
redirected toward lower fertility rates. None of the mechanisms involves
taxation or coercion.
A central plank of family planning programs is the idea of reducing un-
met need. In Section 5 we argue that the methods currently deployed for
measuring unmet need for family planning underestimate it. We also show
that the UN’s Sustainable Development Goals include a measure for judg-
ing the success of family planning programs that potentially creates wrong
incentives for ofcials overseeing the programs. Our analysis reveals that
family planning programs are undervalued by national governments and
international agencies.
By how much? To determine that, we go beyond measuring unmet
need and try to quantify environmental externalities. Estimates of the en-
vironmental externalities traceable to procreation are sparse. Customary
methods for measuring externalities infer people’s willingness to pay for
Nature’s products and services from their behavior or from their expressed
preferences. Those methods are unavailable for reaching global estimates,
nor are they appropriate for the purpose at hand. We circumvent those
problems by studying global statistics on natural capital and identify key
processes that drive the biosphere (Sections 6–7). Such information is not
410 SOCIALLY EMBEDDED PREFERENCES
sufcient for quantifying the benets of family planning programs, but it of-
fers a way to estimate the annual global demand we make of the biosphere
and compare it to the annual global supply. That is done in Section 8, where
we report that demand has for some time exceeded supply. The nding says
we are drawing down natural capital and therefore that environmental ex-
ternalities are substantial.
In Section 9 we provide crude estimates of the size of the global popu-
lation that the biosphere can support at a comfortable standard of living un-
der contemporary technologies and institutions. The gap between the gure
we reach and the current size of the world’s population is substantial. Our
estimate of the gap could be viewed as being an overestimate of what lies in
the future, inasmuch as sustainable population at a comfortable living stan-
dard would be higher if future technological advances economize on the
use of natural capital. On the other hand, our estimate could be viewed as
an underestimate, inasmuch as global population has been projected to rise
to 11.2 billion by the end of the present century and the UN’s Sustainable
Development Goals are simultaneously aimed at signicantly increasing per
capita incomes. Whether resource-saving technological advances are likely
to blunt humanity’s demand for Nature’s products and services even as eco-
nomic activities increase is, of course, a matter of speculation. We therefore
identify reasons why technological changes in the past and the evolution of
our consumption patterns have been rapacious in the use of natural capital.
Those reasons point to policies that would be expected to encourage tech-
nological innovations and lifestyles that place lighter demand on Nature’s
products and services.
The analysis in Sections 8–9 is based on gures using global averages.
Central to the Sustainable Development Goals, however, is poverty allevia-
tion. In Section 10 we study the impact of poverty alleviation measures on
the global demand for Nature’s goods and services. Our analysis uncovers
yet another clash of rights among contemporaries and between present and
future people.
Although the externalities we classify here arise in all contemporary
societies, there is a difference between rich (high-consuming) societies with
low desired family size and poor (low-consuming) societies with high de-
sired family size. Environmental externalities arising from the activities of
people in rich countries are included in our analysis (they are due to the
high consumption enjoyed by new births over their lifetime). Simple cal-
culations show that contemporary global environmental problems cannot
be traced to high fertility in today’s poorest parts of the world. Neverthe-
less, we focus on reproductive behavior in the world’s poorest region, sub-
Saharan Africa, because desired family size there is strikingly large in com-
parison to standards elsewhere and because the costs of the correspond-
ingly high population growth rate can be expected to be borne in great
measure by future Africans themselves. The benets of family planning
AISHA DASGUPTA /PARTHA DASGUPTA 411
programs have been routinely underestimated by the international commu-
nity, but perhaps most conspicuously by governments in sub-Saharan Africa
(Section 11).4
Part I
1. Rights
The legal philosopher Charles Fried distinguished positive rights from nega-
tive rights (Fried 1978). We are to think of positive rights as a claim to some-
thing, a share of material goods or some commodity such as education and
medical attention. A negative right is a right that something not be done to
one, that some particular imposition be withheld. Fried observed that pos-
itive rights are asserted to scarce goods and that scarcity implies a limit to
their claim. He also suggested that negative rights, for example the right not
to be interfered with in forbidden ways, do not appear to have such natu-
ral limitations. (“If I am let alone, the commodity I obtain does not appear
of its nature to be a scarce or limited one. How can we run out of people
not harming each other, not lying to each other, leaving each other alone?”
(p. 110).)5
Fried’s dichotomy is useful for studying the place of rights in family
planning programs, but his suggestion that the exercise of negative rights
does not involve costs is questionable. The claim that one’s proximity should
not be contaminated by cigarette smoke is a negative right, which is vio-
lated when someone smokes in that proximity. To protect that right, gov-
ernments in many countries prohibit people from choosing at will where
they smoke. That represents a cost to smokers. In contrast, a right to exercise
one’s agency would appear to be a positive right (e.g. freedom of speech),
but it does not inevitably demand resources from others. It is not so much
that negative rights do not suffer from resource limitations whereas posi-
tive rights do, it is more that the two sets of rights have separate frames of
reference. The contrasting phrases, right to self-determination and right to
have an imposition withheld, point in different directions.
The 1994 International Conference on Population and Development
reafrmed the language of rights in the sphere of family planning and
reproductive health. The Conference’s conclusions stated: “Reproductive
rights …rest on the recognition of the basic right of all couples and indi-
viduals to decide freely and responsibly the number, spacing, and timing of
their children, and to have information and means to do so, and the right
to attain the highest standards of sexual and reproductive health” (UNFPA
1995: Ch. 7, Sect. 3).
The qualier “responsibly” could be read as requiring couples to take
into account the adverse environmental externalities their reproductive de-
cisions may give rise to; but that probably would be a stretched construction.
412 SOCIALLY EMBEDDED PREFERENCES
Certainly, writings afrming the UN declaration have interpreted the pas-
sage and its intent more narrowly. For example, the fundamental right
of individuals “to decide freely and for themselves whether, when, and
how many children to have” is central to the vision and goals of Family
Planning 2020 (FP2020). It is also pivotal in the reproductive health indi-
cators of the Sustainable Development Goals. Both positive and negative
rights are in play here. Rights to information and other services pertaining
to family planning and reproductive health are positive rights. The right to
choose one’s family size, on the other hand, would appear to be a negative
right.6
Even though Fried’s classication is not without problems, it is use-
ful for studying the relationship between externalities and rights. First, to
insist that the rights of individuals and couples to decide freely the num-
ber of children they produce trump all competing interests is to minimize
the rights of all those (most especially, perhaps, future people) who suffer
from the environmental externalities that accompany additions to the pop-
ulation. Second, UNFPA’s statement ignores the latent need among those
who do not want family planning now but would want it if others among
their peer group were using modern contraceptives. We study the two in
turn.7
2. Ours vs. theirs
That reproductive decisions may involve a clash of rights is not self-evident.
In a powerful essay that dismissed concerns on over-population, Bauer
(1981, pp. 61–64) wrote: “The comparatively high fertility and large families
in many ldcs (less developed countries) should not be regarded as irrational,
abnormal, incomprehensible or unexpected. They accord with the tradition
of most cultures and with the precepts of religious and political leaders. …
Allegations or apprehensions of adverse or even disastrous results of pop-
ulation growth are unfounded. They rest on seriously defective analysis of
the determinants of economic performance; they misconceive the conduct
of the peoples of ldcs; and they employ criteria of welfare so inappropriate
that they register as deterioration changes which are in fact improvements
in the conditions of people.”
One problem with Bauer’s critique is that it gives the impression that
societies in past eras were characterized by large families. But if fertility rates
were high then, so were mortality rates; and high fertility rates are a rational
response to high mortality rates. The contemporary demographic problem
in the world’s poorest regions is that fertility rates remain high even though
mortality rates have fallen considerably. The main problem with Bauer’s
critique, however, is that even when men and women at the household
level prefer large numbers of children to small numbers, it does not follow
there is no resource-allocation failure they themselves would acknowledge
AISHA DASGUPTA /PARTHA DASGUPTA 413
if only they were asked. As in every other eld of personal choice, we should
ask whether a collection of reasoned decisions at the individual level may
harbor collective failure. This is the central question raised by externalities,
and it is particularly apposite in the case of adverse externalities and socially
embedded preferences.
That family planning services bring many benets (health, education,
income, women’s empowerment) to those who make use of them has been
documented repeatedly in recent years (Koenig et al. 1992; Debpuur et al.
2002; Cleland et al. 2006; Cleland et al. 2012; Tsui, McDonald-Mosley, and
Burke 2010; Canning and Schultz 2012; Soneld et al. 2013; Bongaarts
2016; Miller and Babiarz 2016). Our focus on externalities points to the fact
that they bring benets to others as well. Those additional benets should
be included in the design of social policies.
Policies for curbing adverse reproductive externalities can take several
forms. Education, especially female education, is one route; some argue it
is the most effective route (Lutz, Butz, and KC 2014). But that can take
time, and female education is not the only factor driving fertility.8Another
tool involves demonstrative persuasion, which can be attempted through
community discussions on the need for behavioral change. The agent of
persuasion could be the community, NGOs, or the state.9A further tool
is taxation, which permits people to choose as they wish, but at a price.
Although taxation as a device for curbing environmental externalities is fa-
miliar in wealthy countries, it is not available for reducing the demand for
children in poor countries, where the poorest households (who do not pay
taxes) are most often the ones that have the highest demand. A further pol-
icy tool is a quota, such as China’s previous directive of the one-child fam-
ily, or the Chinese government’s recently revised two-children-per-couple
directive.
Quotas are an extreme form of non-linear tax schedule: zero tax up to
the quota, followed by a severe tax beyond it. (The tax need not be mon-
etary; it could be strong collective disapproval.) An alternative to taxing
people if they exceed their quota is to reward them if they stay within it.
We are thinking of quota here in the same way as people think of quo-
tas when they are imposed as food rations in periods of extreme shortage,
compulsory vaccination against communicable diseases, and prohibition on
smoking in public spaces. The rst example ensures equality in the distribu-
tion of a positive right; the second and third examples protect and promote
negative rights.
The classication of externalities suggests a variety of policy tools for
reducing fertility rates. The tools differ in the extent to which the right to
self-determination is compromised. None is likely to prove uncontroversial.
The issues remain unsettled.10
414 SOCIALLY EMBEDDED PREFERENCES
3. The demand for children and African
exceptionalism
Social anthropologists have shown that children are valuable to us not only
because of our innate desire to bear and rear them, but also because they
represent the fulllment of tradition and religious dictates and are the clear-
est avenue to self-transcendence. One such injunction emanates from the
cult of the ancestor, which, taking religion to be the act of reproducing the
lineage, requires women to bear many children.11 This motivation was used
by Caldwell and Caldwell (1990) to explain why sub-Saharan Africa has for
the most part proved so resistant to fertility decline.
A weakness of the argument is that, although it explains why fertil-
ity rates in Africa are high (the total fertility rate is 5.1 today, in contrast
to 2.5 in India, 1.6 in China, and the global TFR of 2.5), it does not ex-
plain why the rates have not responded to declines in infant mortality to
the extent one might have thought on the basis of experience elsewhere.12
Even in sub-Saharan Africa fertility rates have been lower than the maxi-
mum possible. Below we study possible reasons why the response has been
slower than expected. We should expect the reasons to vary across regions
within the sub-continent. Under increasing urbanization some will have
also weakened over time (e.g. the cult of the ancestor). But because quan-
titative evidence on their relative signicance across regions is patchy, we
only identify them here.
In places where formal institutions are underdeveloped, children also
substitute for other assets and are thus also valuable for the many bene-
ts they bring to their parents. This is most apparent in the poorest regions
of the world. Children serve as security in old age in places that have nei-
ther pension schemes nor adequate land markets. They are also a source of
labor in households possessing few labor-saving devices. Children mind
their siblings, tend to domestic animals, pick berries and herbs, collect re-
wood, draw water, and help with food preparation. The need for additional
hands is especially strong among rural communities in dry and semi-arid re-
gions. Children in poor countries are valued by their parents also as capital
and producer goods.
Caldwell (1981, 1982) proposed that the inter-generational transfer of
resources is from children to parents in poor societies, and from parents to
children in rich societies. The suggestion has been easier to conrm in rich
countries, where the rate of investment in children’s education has been
found to be as high as 6–7 percent of GDP (Haveman and Wolfe 1995).
Conrming the reverse ow in poor countries has been a lot harder, in part
because data are sparse but in part also because even within poor regions
there are signicant differences in attitudes toward reproduction. Those dif-
ferences are traceable to kinship structures, marriage practices, and rules of
inheritance. The implied line of thinking says that over the long run it is
AISHA DASGUPTA /PARTHA DASGUPTA 415
differences in institutions and social norms—originating perhaps in some
measure in geography—that lie behind differences in reproductive behavior
among groups. Theoretical models have been built on the premise that insti-
tutional failure, broadly dened, is the deep cause of pronatalism. Causality
is not traced to differences in income or wealth. It is not that fertility and
mortality rates are high and health status and education attainments are low
in poor regions because people there are poor, it is that very low incomes
go hand in hand with those other features of life. Each variable inuences
the others over time; in the long run they are mutually determined.13
A potential source of reproductive externality is the wedge between
the private and social costs of childrearing. The costs borne by parents are
lower when childrearing is shared among kin than when households are
nuclear. In sub-Saharan Africa fosterage within the kinship is a common-
place. Children are not raised solely by their parents; the responsibility is
more diffuse within the kinship group (Caldwell 1991; Bledsoe 1990, 1994).
In parts of West Africa up to half the children have been found to be living
with their kin at any given time. Nephews and nieces have the same rights
of accommodation and support as do biological offspring. There is a sense
in which children are seen as a common responsibility, which makes it im-
portant that in surveys that seek to identify desired numbers of children it
is made clear that the questionnaire refers to biological children. However,
fosterage creates a free-rider problem if the parents’ share of the benets
from having children exceeds their share of the costs. The corresponding
externalities are conned to the kinship. Other things equal, reduction in
those externalities would be accompanied by a fall in the demand for chil-
dren and all households would benet.14
Related to this is a phenomenon observed by Guyer (1994) in a Yoruba
area of Nigeria. In the face of deteriorating economic circumstances, some
women bear children by different men so as to create immediate lateral
links with them. Polyandrous motherhood enables women to have access
to more than one resource network. Children are a further form of wealth
for their mothers; desired fertility is consequently higher.
The idea of wealth-in-people has been developed by anthropologists to
reect the additional status and other social advantages that are conferred
on women (more generally, households) in African societies by having chil-
dren (Guyer and Eno Belinga 1995). There is formal resemblance here to
Veblen’s account of status in an entirely different context, namely, conspic-
uous consumption in the Gilded Age in America. In the present context,
desired fertility is higher because of the competition generated by the de-
sire for status, and it leads to a collective loss in well-being.
Communal land tenure of the lineage social structure in sub-Saharan
Africa has offered an inducement for men to procreate: a larger family can
claim a greater amount of land. In addition, conjugal bonds are frequently
weak, so fathers often do not bear their fair share of the costs of siring a child.
416 SOCIALLY EMBEDDED PREFERENCES
Anthropologists have observed that the unit of African society is a woman
and her children, rather than parents and their children. Frequently, there is
no common budget for the man and woman. Descent in sub-Saharan Africa
is, for the most part, patrilineal and residence is patrilocal. That suppresses
women’s voice; and because women bear a disproportionate share of the
costs of reproduction, it raises the fertility rate. Taken together, patrilineal-
ity, weak conjugal bonds, communal land tenure, and a strong kinship child
support system have been broad characteristics of the region. They provide a
powerful stimulus to fertility. Admittedly, patrilineality and patrilocality are
features of the northern parts of the Indian sub-continent also. But conju-
gal bonds there are substantially greater. Moreover, since agricultural land
is not communally held, large family sizes lead to fragmentation of land-
holdings. In contrast, large families in sub-Saharan Africa are (or, at least
were, until recently) rewarded by a greater share of land belonging to the
lineage or clan.15
4. Socially embedded preference structures and
conformism
That children are a parental end (and not just a means toward other parental
goals) provides a potentially powerful mechanism by which reasoned fer-
tility decisions at the level of every household could lead to an unsatisfac-
tory outcome from the perspectives of all households. The mechanism arises
from the possibility that traditional practice is perpetuated by conformity.
Reproductive decisions are not only a private matter; they are subject to
social mores, which in turn are inuenced by family experiences and the
cultural milieu. But social mores are shaped by the behavior of all. There is
circularity in this, which we can unravel by supposing that household pref-
erence structures are socially embedded. Behavior is conformist when the
family size that each household desires is positively related to the average
family size in the community (Dasgupta 1993: Ch. 12).
Douglas and Ney (1998) regard consumption as an expression of social
engagement. Taken literally that would appear odd, but what the authors
were pointing to is that a meal taken alone is different from a meal enjoyed
in the company of others. Fads and fashion may be short-run expressions
of social engagement (we refer to such expressions as conformism); what
Douglas and Ney showed us is that our need to belong is deep and endur-
ing. We rely on one another for safety, consolation, information, compan-
ionship, and governance. Many of our actions are undertaken in a social
setting, and all of our actions are inuenced in part by attention to others.
Whatever the basis of conformism, there would be practices encourag-
ing high fertility that no household would unilaterally desire to break. Such
practices could have had a rationale in the past, when mortality rates were
high, population densities were low, natural resources were plentiful, the
AISHA DASGUPTA /PARTHA DASGUPTA 417
FIGURE 1 Socially embedded preferences for children
•••
•
•
•
A
B
C
DE
F
O n1 n2 n3 n
Household’s desired number of children
(TFR)
threat of extermination from outside attack was large, and mobility was re-
stricted. But practices can survive even when their original purposes have
disappeared. One reason they can survive is that if all other households
continue to follow the practice and aim at large family sizes, no conformist
household would on its own wish to deviate from the practice; however, if
all other households were to restrict their fertility, every household would
wish to restrict its fertility as well. Conformism can thus be a reason for the
existence of multiple social equilibria. A society could get embedded in a
self-sustaining mode of behavior characterized by high fertility and low ed-
ucational attainment, even when there is another potentially self-sustaining
mode of behavior characterized by low fertility and high educational at-
tainment and which is preferred by all. Economists think of an economy
becoming stuck in a low-level equilibrium for lack of a “big push,” which,
if only it would happen, would move them to a higher-level equilibrium.
Big push is not to be identied with government at. Below we see that
societies can experience big pushes from unexpected sources.
Socially embedded preferences for children are shown in Figure 1.
The curve ABCDE is the representative household’s desired number of chil-
dren, plotted against the average number of children per household (the
418 SOCIALLY EMBEDDED PREFERENCES
horizontal axis). The curve is upward sloping and intersects the 45oline OF
at three points: B, C, D. Each is a social equilibrium, at TFRs n1,n2, and
n3respectively. To interpret ABCDE with concrete numbers, imagine that
each household regards 5 to be the ideal number of children if all other
households have 5 children (n3on the horizontal axis)); 4 to be the ideal
number if all others have 4 (n2); and 2 to be the ideal number if all others
have 2 (n1). Imagine now that each household prefers the outcome where
all households have 2 children. It can nevertheless be that their society is
stuck in a situation where each household has 5 children. It can get stuck
because no household would have a reason to deviate from 5 if all other
households have 5; which is another way of saying that 5 is a self-enforcing
choice. It is easy to conrm that both 2 and 5 are stable equilibria, in that
a small deviation from 2 (or from 5) would in time return to a situation
where each household chooses 2 (or 5). It follows that 5 would be just as
tenacious a TFR as 2.16
That does not mean society would be stuck at 5 forever. As always,
people differ in the extent of their absorption of traditional practice. There
would inevitably be those who experiment, take risks, and refrain from join-
ing the crowd. They are the tradition-breakers, and they often lead the way.
Educated women are among the rst to make the move toward smaller
families.17 A possibly even stronger pathway is the inuence that newspa-
pers, radio, television, and now the internet play in transmitting informa-
tion about other lifestyles (Freedman 1995 was one of the rst to detect
that pathway). The media could be a vehicle by which conformism increas-
ingly becomes based on the behavior of a wider population than the local
community (the peer group widens). And that disrupts behavior.18
A number of studies on fertility point to choices that are guided in part
by attention to others. In her highly original work on demographic change
in Western Europe over the period 1870–1960, Watkins (1990) showed that
differences in fertility and nuptiality within each country declined. She also
found that in 1870, before the large-scale declines in marital fertility had be-
gun in most areas of Western Europe, demographic behavior differed con-
siderably within countries. Differences among provinces within a country
were high even while differences within provinces were low. Spatial be-
havioral clumps suggest the important inuence of local communities on
behavior. In 1960 differences within each country were considerably less
than in 1870. Watkins explained this by increases in the geographical reach
national governments achieved over the 90 years in question. The growth
of national languages could have been the medium through which repro-
ductive behavior was able to spread.
Watkins’s study was historical, as were the studies Montgomery and
Casterline (1998) used to distinguish pathways by which reproductive prac-
tices diffuse within a society. In a commentary on West Bengal, where fer-
tility rates declined in the early 1970s ahead of the northern states of India
AISHA DASGUPTA /PARTHA DASGUPTA 419
and neighboring Bangladesh, Basu and Amin (2000) attributed the West
Bengal experience to historical and cultural factors there that combined to
promote interaction between the elite and the general public. Jensen and
Oster (2009) in contrast have studied a natural experiment. They found that
state-level fertility rates declined in step following the staggered introduc-
tion of cable TV in Indian states.19
A feature of historical studies of the diffusion of behavior across space
and time is that they do not necessarily identify the behavioral fundamen-
tals (or “drivers”) on which the diffusion process is built. They also differ
from one another in terms of the transmission mechanism. The drivers
could be knowledge acquisition, or they could be pure mimicry, or what
Cleland and Wilson (1987) called “ideation,” or the advent of modernity,
or the desire to belong to one’s (possibly expanding) group, or the force
of celebrity culture, and so on. These fundamentals are not unrelated, but
they are not the same. Regarding transmission mechanisms, it could be
that people observe successful behavior and copy it, or that the language
in which newspapers are read spreads, or that people discuss and debate
among themselves, and so forth.20
The model in Figure 1 is built on the common structure of all such
diffusion processes. Studying the common structure offers the advantage
that we are able to analyze the resting (i.e., equilibrium) points of a wide
variety of diffusion processes without having to identify the processes them-
selves. Our model assumes that fertility preferences are socially embedded,
but it does not specify the reasons households are inuenced by the behav-
ior of others. Being analytical, the model is able to entertain counterfactu-
als. It allows us to ask how a household’s behavior would differ if the social
parameters underlying the curve ABCDE were to be otherwise. This is a
necessary exercise in policy analysis, because policies can be used to shift
the curve ABCDE (and therefore the equilibrium points n1,n2, and n3)as
well as to inuence the beliefs on the basis of which households act. The
common structure also tells us that fertility transitions can be interpreted as
disequilibrium phenomena (Dasgupta 2002), where practices change slowly
in response to gradual changes in the social environment, until a tipping
point is reached from which society shifts rapidly to a new stable equilib-
rium, say from high fertility to low fertility.
The common structure of diffusion processes that we are studying
proves useful also for interpreting statistical regularities between actual fer-
tility (TFR) and wanted fertility (WTFR). Pritchett (1994), for example, re-
gressed TFR on WTFR in 43 countries in Asia, Africa, and Latin America
and found that about 90 percent of cross-country differences in TFR are as-
sociated with differences in WTFR. He also found that excess fertility (TFR
– WTFR) was not systematically related to actual TFR, nor an important
determinant of it.
420 SOCIALLY EMBEDDED PREFERENCES
Pritchett concluded that high fertility is due entirely to the strong de-
sire for children. Our model draws a different conclusion. That fertility
preferences are socially embedded tells us we should expect the correla-
tion Pritchett obtained, but it also warns us not to attribute causality to the
relationship. It would be as true to say fertility rates in those countries where
they are high are high because people have a strong desire for children as
it would be to say that people there have a strong desire to have children
because fertility rates are high.
5. Unmet need, desired family size, and the UN’s
Sustainable Development Goals
UNFPA (1995) took it that family planning and reproductive health policies
should address unmet need, meaning that they should be made to serve
women aged 15–49 who are seeking to stop or delay childbearing but are
not using modern forms of contraception (Bradley et al. 2012; Alkema et al.
2013). Although the idea of unmet need could appear straightforward, it
has in practice been interpreted in different ways over the years. It is cur-
rently measured using more than 15 survey questions, including questions
on contraceptive use, fertility intentions, pregnancies, postpartum amen-
orrhea, sexual activity, birth history, and menstruation. Women’s reported
fertility intentions are inferred from such questions as: “Now, I have some
questions about the future. Would you like to have a(nother) child or would
you prefer not to have (any more) children?” This is followed by a question
about how long the woman wants to wait if she responded to the previous
question that she does want a(nother) child.21
There are deep problems here. Unmet need as calculated is based on
the respondent’s expressed wants for children, and—taken together with
responses to other questions—this response is used to infer unmet need for
family planning. But in matters of life and death, resource needs assume an
independent status; they even serve as the basis on which commodity rights
are founded. The philosopher David Wiggins has argued that a statement of
the form “person A needs commodity X” is tantamount to a challenge to
imagine an alternative future in which A escapes harm without X (Wiggins
1987, p. 22). Expressed wants or desires for children—used to calculate un-
met need for family planning—may not adequately convey her true need
for family planning, that is, for her own best interests. A poor woman, suf-
fering from iron deciency and living in a setting where she is compelled to
have sex and bear children, has a need for contraception for her own ben-
et that could remain undetected in her responses to questions regarding
her desire for children. To infer needs solely from wants is therefore to un-
dervalue the signicance of family planning. Moreover, none of the survey
questions is conditioned on the behavior of others.
AISHA DASGUPTA /PARTHA DASGUPTA 421
Closely related to wants and desires is the notion of desired family size,
which is obtained from answers to the following question: “If you could go
back to the time when you did not have any children and could choose ex-
actly the number of children to have in your whole life, how many would
that be?” The wanted total fertility rate is calculated by rst dividing the
number of observed births into those that occurred before and after the
desired family size is reached (the former are considered as wanted,
the latter unwanted). WTFR is then obtained with the same procedure as
the one used in calculating TFR (that is, from age-specic fertility rates), but
only wanted births are included in the numerator of these rates.
There are dangers of biases in responses to the question at the basis
of desired family size, but the need for family planning programs to have
quantitative estimates of it is clear enough. Notice, though, that the ques-
tionnaire does not ask a woman what her desire would be if the prevailing
fertility practices of others were different. In fact there is no mention of the
prevailing fertility rate. Since respondents are not invited to disclose their
conditional desires, it is most likely they disclose their desired family size on
the assumption that fertility will remain at its prevailing rate. A direct way to
discover socially embedded preferences would be to reconstruct the ques-
tionnaires by asking a series of conditional questions, which we collapse
here for convenience into one: “If you could go back to the time when you
did not have any children and could choose exactly the number of children
to have in your whole life, how many would that be, assuming everyone
else in your community had nchildren over their whole life?”
The survey could pose the conditional question in an ascending order
of n, say from 0 to 10. The example in Figure 1 imagines that the answers
to n=2, 4, and 5 are, respectively, 2, 4, and 5. It also imagines that answers
to the questions in which n=0, 1, 3, 6–10, respectively, differ from 0, 1, 3,
6–10; which is why the latter numbers are not social equilibria. No doubt
responding to a string of conditional questions would tax respondents, but
not to ask them is to misread fertility desires.22
Fabic et al. (2015) dened total demand for modern contraception to
be the number of women who want to delay or limit childbearing (i.e., the
sum of contraceptive users and women with unmet need). The role of fam-
ily planning, the authors argued, is to supply that demand. The suggestion is
that the success of family planning should be measured by the ratio of fam-
ily planning users to the total demand. The United Nations has adopted this
measure in its Sustainable Development Goal 3.7.1. It is known as “demand
for family planning met with modern contraceptive methods,” or “demand
satised” for short. Formally, if Xis the number of women aged 15–49 who
are users of modern contraceptives, Yis the number of women with unmet
need, and Zis total demand for modern contraception, then Z=X+Yand
the UN’s “demand satised” is X/Z=X/(X+Y).
422 SOCIALLY EMBEDDED PREFERENCES
Reproductive rights are at the heart of X/Z, which is its attraction. The
indicator reects voluntarism, rights and equity, informed choice, and the
imperative of satisfying individuals’ and couples’ own choices with regard
to the timing and number of children. But there are problems. The use of
demand satised as the measure of success could create perverse incen-
tives among programs managers. A program’s performance would improve
if more women were to declare that they want to get pregnant. As long as
women want many children, Y(unmet need) remains small, and therefore
Z(total demand) is only marginally greater than X(the number of modern
contraceptive users). The country scores well on the indicator demand sat-
ised and appears not to need further family planning program effort. The
success could mask a situation where contraceptive use is low and stagnant
and high fertility rates persist. Moreover, as we saw in Section 4, fertility
preferences, which contribute to the measurement of Y, are themselves in-
uenced by the behavior of others. Ycould therefore be small in a society
that harbors another equilibrium in which Yis large.
The concept of reproductive rights, as currently framed, undervalues
family planning. There are collective benets to be enjoyed if members of
a community are enabled to alter their fertility desires in a coordinated
manner. Family planning can help to bring about changes in such social
norms. Our analysis does not run against rights as a plank for family plan-
ning; it expands the sphere in which rights are acknowledged, protected,
and promoted.23
Part II
6. The biosphere as an open-access resource
To the best of our knowledge there are no national estimates of the environ-
mental benets of family planning. So we make a direct approach to esti-
mating the benets by reviewing humanity’s demand for ecological services
at the global level. For that purpose it proves useful to regard the biosphere
as a single renewable natural resource. This requires a heroic aggregation
exercise, in which billions of assets are aggregated into a single measure.
If that seems an absurd undertaking, we should recall that global sheries
and forest biomes are routinely measured in units of biomass, which also
involves giant aggregation exercises. No doubt problems of aggregation are
magnied when we study the biosphere as a whole, but they are not mag-
nied that much in complexity.
One reason the biosphere is hard to aggregate is that the biogeochem-
ical processes that shape natural capital differ widely in both speed and
spatial reach. Since most global environmental resources have no prices
attached to them (there is an absence of property rights to open-access re-
sources), indirect methods have to be found in order to obtain notional
AISHA DASGUPTA /PARTHA DASGUPTA 423
prices that reect their scarcity value (what economists call shadow prices)
for them. Nevertheless, there is no escaping the need for imagining the bio-
sphere as a gigantic piece of natural capital if we are to discuss the adverse
environmental externalities accompanying births. We denote the aggregate
stock of the biosphere by K.Kmay alternatively be called the global stock
of natural capital.
A concrete way to imagine the biosphere is to focus on its biomass.
In that case K, measured in units of biomass, is the state variable of the
biosphere. The composition of biomass (grasslands differ from agricultural
elds) is reected in the aggregate measure K.LetK(t) be the biomass at time
t, and let F(K(t)) be the net output of biomass over a brief interval of time
(say, a year), starting at t.F(K) is a ow or ux (so many units of biomass
per year), whereas Kis a stock (so many units of biomass). Ecologists call
F“net primary production.” When the occasion demands, we will refer to
Fas “ecosystem services.”
To imagine the biosphere as a renewable natural resource requires fac-
ing a further problem. Even 2,000 years ago, when global population was
under 250 million and per capita income a bit over a dollar a day (Maddison
2001), a reasonable approximation would have been to treat humanity as
a separate entity from the biosphere. Today it is no longer possible to do
so. We are much engaged in transforming the biosphere, by both creating
biomass and destroying it. So we have to imagine humanity as being at the
same time a constituent of the biosphere and an entity separate from it. No
doubt that is a stretch, but it is possible to do it without running into con-
tradictions. We avoid contradiction by noting that a portion of F(K), say α,
is needed for the maintenance of the biosphere. So if, over a period of time,
F(K) was usurped entirely by humanity, Kwould shrink and biodiversity
would be reduced. If during an interval of time, humanity was to consume
even more than F(K), Kwould shrink even more, further drawing down
biodiversity. Humanity is consuming at that level now, which is what has
led Wilson (2016) to propose that we should leave half the biosphere alone.
(1–α)F(K) should therefore be interpreted as the usable ow of biomass;
usable, that is, by humanity.24
One might think that F(K) must be an increasing function of Kfor
all values of K, but that would be to overlook that Earth is nite in extent.
Fshould therefore be taken to be an increasing function of Kfor small values
of K, but a declining function of Kfor large values of K. Earth’s carrying
capacity for the prevailing life forms (a formidable notion in itself, but one
that cannot be avoided) is that positive value of Kat which F(K) is zero.25
7. Ecosystem losses in the Anthropocene
Humanity’s success in raising the standard of living over the past 250 years
has involved creating and then using ideas and accumulating reproducible
424 SOCIALLY EMBEDDED PREFERENCES
(or manufactured) capital and human capital, while mining and degrading
K. The socioeconomic processes that drive the production, dissemination,
and use of ideas and the accumulation of reproducible and human capital
are at the heart of modern growth and development economics, but the
decumulation of natural capital has remained unrecognized (e.g., Helpman
2004). The decumulation is also unrecorded in ofcial economic statistics.
This bias is not a reection of an indifference to the natural world; it
is more a disconnect between the social and environmental sciences. It is
widely known, for example, that even while industrial output increased by
a multiple of 40 during the twentieth century, the use of energy increased by
a multiple of 16 (contributing to climate change and degrading the oceans),
the methane-producing cattle population grew in pace with human popu-
lation (contributing to climate change and degrading the oceans), and sh
catch increased by a multiple of 35 (reducing stocks in the open seas).26
Environmental scientists have found that the application of nitrogen to the
terrestrial environment from the use of fertilizers, fossil fuels, and legumi-
nous crops is now at least as great as that from all natural sources com-
bined. They have also found that soil nitrogen and phosphorus inventories
have doubled over the past century (nitrate levels in Greenland ice today
are higher than at any time in the previous 100,000 years) and that 25–
30 percent of some 130 billion metric tons of carbon harnessed annually
by terrestrial photosynthesis is now appropriated for human use (Vitousek
et al. 1986; Vitousek et al. 1997; Haberl et al. 2007). That signals the stupen-
dous presence of a single species and helps to explain why extinction rates
of species since the early modern era have been far above background rates
and have increased much further since the nineteenth century (RSPB et al.
2013). These gures all point to rates of biomass transformation in excess
of the usable ux, (1–α)F(K). Consequently, they point to reductions in K.
The Millennium Ecosystem Assessment (MEA 2005a–d) reported that
15 of the 24 ecosystems the authors had investigated worldwide are either
degraded or are being exploited at unsustainable rates. Population pressure
on land and the habitat destruction that accompanies human encroachment
are the proximate causes. The gures put the scale of humanity’s presence
on the planet in perspective and record that we are now Earth’s dominant
species (Ehrlich and Ehrlich 2008). The statistics also explain why our epoch
has now been named the Anthropocene.27
8. Net demand on the biosphere
Studying biogeochemical signatures of the past 11,000 years, Waters et al.
(2016) have provided a sketch of the human-induced evolution of, among
other signatures on the biosphere, soil nitrogen and phosphorus inventories
in sediments and ice. The authors reported a sharp increase in their inven-
tories in the middle of the twentieth century. Their work shows that the
AISHA DASGUPTA /PARTHA DASGUPTA 425
now-famous gure of the “hockey stick” that characterizes time series of
carbon concentration in the atmosphere also characterizes a broad class
of geochemical signatures and signals a sharp increase in the rate of de-
terioration of Earth’s life-support system. Biological extinctions, rises in
greenhouse gas concentrations, contamination of marine species with per-
sistent pollutants, nutrient overload in soil and water, and oceanic dead
zones are but ve signatures of those stresses. Waters et al. proposed that
mid-twentieth century should be regarded as the time we entered the
Anthropocene.28
Their reading is consistent with macroeconomic statistics. World pop-
ulation in 1950 was 2.5 billion, global GDP a bit over 7.5 trillion interna-
tional dollars (at 2015 prices). The average person in the world was poor,
with an annual income of a bit over 3,000 international dollars. Since then,
the world has prospered materially beyond recognition. Population has in-
creased to 7.4 billion and world output of nal goods and services today
is about 110 trillion international dollars, meaning that world income per
capita now is about 15,000 international dollars. A 15-fold increase in global
output over a 65-year period not only helps to explain the stresses to the
Earth system that we have just reviewed, but also hints at the possibility that
humanity’s extraction of biomass has for some time exceeded sustainable
levels. So, in addition to the direct benets of family planning programs,
which are currently assessed according to the extent to which reproductive
rights are met, we should estimate the decline in reductions in Kowing to a
prevented birth and place a value on that reduction. If the reduction is esti-
mated to be Kper prevented birth and the social value of a unit of natural
capital is Q, then the environmental benets from a family planning pro-
gram would be the product of QKand the number of births the program
is expected to prevent.29
In the eld of family planning nothing is simple. Addressing one prob-
lem simply leads to several more. If Qremains largely unestimated by
economists, determining Kfrom a prevented birth poses problems for the
demographer. Some family planning on the part of women involves delay-
ing births, not limiting numbers. Better spacing is a good in itself, but if
numbers are not affected, the environmental consequences would be slight
(Kwould be negligible).
In a review of the state of the Earth’s life-support system, WWF (2012)
reported that in the early years of this century, humanity’s demand for eco-
logical services exceeded by 50 percent the rate at which the biosphere is
able to supply those services. The gure is based on the idea of a “global
ecological footprint,” which is the surface area of biologically productive
land and sea needed to supply the resources a human population consumes
(food, bers, wood, water) and to assimilate the waste it produces (materi-
als, gases). The Global Footprint Network (GFN) regularly updates its esti-
mates of the global ecological footprint.30 A footprint in excess of 1 means
426 SOCIALLY EMBEDDED PREFERENCES
demand for ecological services exceeds their supply. GFN’s most recent
estimate is a footprint of a bit over 1.6, which in our terminology means
humanity has in recent years been consuming ecological services at the rate
1.6(1–α)F(K). Humanity’s demand for ecological services can exceed supply
for a period, but not indenitely. Our model would interpret a footprint in
excess of 1 as a decline in K(i.e., K<0). Sustainable development would
require that the footprint over time must on average equal 1. To be sure,
the entire function F(K) can be made to increase by measures that reduce
the footprint to less than 1. Advances in biotechnology, for example, are
designed to increase F(K). But the advances would be successful only if
they do not have large unintended adverse consequences for the biosphere.
Moreover, irreversible losses, arising say from biological extinctions (de-
clines in K), would act as constraints on the biosphere’s ability to recover.
Moves toward consumption and production practices that make smaller de-
mands on the biosphere would be a more direct approach to reducing our
impact on the Earth system. We return to those possibilities in Section 11.
The greatest contributors to the ecological-footprint overshoot are the
OECD countries. Estimating national footprints poses enormous conceptual
and practical difculties; and without notional shadow prices to guide us,
it is impossible to estimate the value of environmental externalities asso-
ciated with an average new birth. But for the global economy the matter
is less opaque because errors in measuring national footprints that arise on
account of trade in goods and services would cancel in the aggregate.
Assuming that the global ecological footprint is 1.6, we may conclude
that to maintain the current global average living standard at the prevailing
distribution of income, we would need 1.6 Earths. It is against this back-
ground that we offer a quantitative account of the adverse environmental
externalities humanity is inicting on itself by allowing a substantial por-
tion of Nature’s goods and services to be free. No doubt estimates of global
ecological footprint are very crude. Moreover, in contrast to estimates of
such development indicators as GDP, population size, life expectancy, and
literacy, which are made by a multitude of national and global institutions,
we are obliged here to rely on the estimates of a solitary research group
(albeit aided by a wide network of ecologists and environmental scientists).
Nevertheless, that there is an overshoot (an ecological footprint in excess
of 1) is entirely consistent with a wide range of evidence on the state of the
biosphere, some of which we have reviewed here. Since the gures are the
only ones on offer, we make use of them.
9. How many people can Earth support in comfort?
Ecologists estimating sustainable world populations have sought to calculate
the human numbers Earth can support at a reasonable standard of living.
Daily, Ehrlich, and Ehrlich (1994) quantied the stresses to the biosphere
AISHA DASGUPTA /PARTHA DASGUPTA 427
that are being caused by humanity’s use of energy. In the early 1990s world
population was 5.5 billion and global energy consumption was an annual
13 terawatts (13 trillion watts). The authors assumed that an annual con-
sumption of 13 terawatts of energy is unsustainable (it would play havoc
with K). As we now know from the work of climate scientists, their pre-
sumption was right. The authors noted the vast differences in energy use
between the world’s rich and poor, but on assuming an equitable distri-
bution of energy use, they estimated that a population of 2 billion (world
population in the early 1930s) could enjoy a comfortable life based on an
annual 3 terawatts of energy consumption; and that a population of 1.5 bil-
lion (world population at the start of the twentieth century) could enjoy
an even more comfortable life based on an annual 4.5 terawatts of energy
consumption.31 Those estimates were a rst cut on a neglected problem. An
alternative procedure is to identify a standard of living that can be justied
on grounds that it supports a high quality of life—we identify one from sur-
veys on “reported happiness”—and ask how many people can be supported
at that quality of life.32
An analysis of one set of global surveys on happiness and their rela-
tionship with household incomes has revealed that in countries where per
capita income exceeds 20,000 international dollars, additional income is not
statistically related to greater reported happiness.33 We work with that g-
ure, even though we are not at all sanguine we understand the nding;
20,000 international dollars is the per capita income in Panama, Mauritius,
and Uruguay today, and it is hard to imagine that happiness hits a road-
block at that level. On the other hand, 20,000 international dollars (at 2015
prices) was the per capita income in the early 1980s in today’s high-income
countries. Were people there on average less happy then than they are now?
The matter remains unclear. So, for want of price estimates of natural capital
(Q), we follow the lead of studies on reported happiness.
World income (or global GDP) today is about 110 trillion international
dollars. Using 1.6 as the gure for the global ecological footprint today and
assuming that the demand on ecological products and services is propor-
tional to GDP, we conclude that sustainable world GDP is an annual 110
trillion/1.6 international dollars; that is, 70 trillion international dollars.
That level of global economic activity would be sustainable because Kwould
not decline. If we now regard 20,000 international dollars as the desired
standard of living for the average person, maximum sustainable population
comes to 3.5 billion.
This estimate is close to the ones obtained by Daily, Ehrlich, and
Ehrlich. Both estimates arrive at a global population under half of what
it is today. This suggests that under current technologies and institutions,
the Earth system offers tight bounds on global population if a comfortable
living standard is to be sustained. World population was about 3 billion in
the 1960s, so we are not talking of unfamiliar gures. But suppose our goal
428 SOCIALLY EMBEDDED PREFERENCES
was less demanding; suppose humanity would be content with an average
income of 10,000 international dollars, which is below today’s global per
capita income.34 Sustainable global population would then be 7 billion. As
noted earlier, we are now 7.4 billion in numbers, moving toward a possible
gure of 11.2 billion in the year 2100. And we have not built into the anal-
ysis deep inequalities in living standards and the human migrations that are
often a response to the distress to which they give rise. We turn to that topic
now.
10. Poverty and the distribution of global income
By the Global Footprint Network’s reckoning, the world’s ecological foot-
print in 1960 was about 0.6. The gure suggests that humanity’s reliance
on the biosphere in 1960 was sustainable and that the biosphere’s compo-
sition was much different then from what it is now. World population in
1960 was about 3 billion and per capita income approximately 4,500 in-
ternational dollars. These statistics are consistent with the nding that the
Anthropocene is only a couple of generations old.
Central to the UN’s Sustainable Development Goals is the elimina-
tion of deep poverty and reductions in global wealth inequality. How does
the balance of rights change when we cease talking exclusively in terms of
global averages? Most economists believe that success in reducing the pro-
portion of the world’s population in absolute poverty from 37 percent in
1990 to just over 10 percent today can be traced to strong growth in GDP
that prominent developing countries (China and India in particular) have
enjoyed since then and the investment in health and education that such
growth made possible.35 It is today almost universally taken as given (e.g.,
Jamison et al. 2013) that eliminating absolute poverty and narrowing health
disparities require robust growth in GDP. But based as it is on market prices,
GDP is insensitive to consumption and production externalities; nor does it
record the depreciation of natural capital that accompanies economic activ-
ity. As the currency in which to measure the sustainability of development
programs, GDP should be abandoned.
Related to poverty and inequalities in living standards is the question
whether the global ecological footprint is proportional to world GDP. In our
previous calculation we assumed the answer is yes. The assumption requires
that household footprint is proportional to household income; that is, the
composition of household expenditure does not matter to the biosphere.
That assumption is in all probability incorrect (Liu et al. 2003). Consider
by way of example the case where the ecological footprint increases less
than proportionately with income. If the distribution of income remains
the same, growth in global GDP by gpercent would be accompanied by a
less than gpercent growth in the demand for ecological services. And that
is a good outcome.36
AISHA DASGUPTA /PARTHA DASGUPTA 429
But what if absolute poverty were to be eliminated by a redistribu-
tion of incomes toward greater equality? Such a policy has strong appeal
to egalitarian convictions. But policymakers would be faced with a cruel
dilemma: even if average income were to remain the same, the demand
for ecological services would increase. That means improving the distribu-
tion of income among today’s contemporaries, a good thing in itself, would
worsen the economic prospects of future generations. There is a clash here
between present and future rights.37
If the ecological footprint increases more than proportionately with
income, our conclusions are reversed. Equalizing incomes among contem-
poraries would improve the economic prospects of future generations, but
agpercent growth in global GDP would be accompanied by a more than
gpercent growth in the demand for ecological services.38 Either way, the
environmental consequences of growth and distribution point in opposite
directions. That is another problem for the hapless policymaker.
11. Dilemmas
The clash of rights we have identied in this essay arises from the fact that
much of the biosphere is treated as a free good. Imagine it were possible to
establish international agreements on policies under which the private costs
of using Nature’s goods and services are something like their social scarcity
values. If that were to come about, environmental externalities associated
with consumption and reproduction would be eliminated, and policies that
address socially embedded preferences could be used to further reduce the
demands we make on Nature, perhaps even to the point where our de-
mands are sustainable.
An additional route to sustainable dependence on the biosphere is
technological progress. Economic historians of the Industrial Revolution
point to the role institutions have played in providing incentives to cre-
ate the technological innovations that have been responsible for reducing
natural resource constraints.39 Looking into the future, though, the rate
of resource-saving technological progress has to be large enough to substi-
tute for rising consumption levels. Otherwise our ecological footprint will
not decline to 1 (a prerequisite for sustainable development). But we can
be optimistic about the character of technological advances and the con-
sumption patterns we correspondingly adopt only if natural capital is priced
appropriately. Understandably, entrepreneurs economize on the expensive
factors of production, not the cheap ones. As long as Nature’s goods and ser-
vices remain underpriced, technological advances and our lifestyles can be
expected to be biased toward their use. Moreover, technological advances
that are patently good can have side effects that are not benign. The ability
to use fossil-based energy at large scales has transformed lives for the bet-
ter, but it has created the unintended consequence of global climate change.
430 SOCIALLY EMBEDDED PREFERENCES
Bulldozers and chain saws enable people to deforest land at rates that would
have been unimaginable 250 years ago, and modern shing technology to
devastate large swathes of sea beds in a manner unthinkable in the past. If
technological progress is our hope, it has to come allied with elimination of
environmental externalities.
The World Bank in its 2016 World Development Indicators reports that
the 1.4 billion people living in high-income countries enjoy a per capita in-
come of 40,700 international dollars. Thus the richest 19 percent of the
world’s population consume about 51 percent of world income (57 tril-
lion/110 trillion). Assuming humanity’s impact on the biosphere is propor-
tional to incomes, 51 percent of that impact can be attributed to 19 percent
of world population. If the UN’s Sustainable Development Goals are to be
met, resource-intensive consumption patterns in these countries have to
decline substantially. Our calculations in the previous section suggest that,
otherwise, efforts to shrink global income inequalities will be unsustainable.
Consumption behavior is inuenced both by our urge to compete with oth-
ers (Veblen’s “conspicuous consumption”) and by our innate desire to con-
form. Each is a reection of socially embedded consumption preferences.
Since both drivers give rise to consumption externalities, the psychological
cost to a person of a collective reduction in consumption is likely to be far
less than it would be if he were to reduce consumption unilaterally. The ag-
gregate cost could even be negative, especially if the working poor were less
poor relative to the working rich, as the former are far greater in number.
To see the numbers involved, recall that in Section 9 we noted that one
set of global surveys on stated happiness and their relationship with house-
hold incomes revealed that in countries where per capita income exceeds
20,000 international dollars, additional income is not statistically related to
greater reported happiness. Imagine that the 1.4 billion people in today’s
high-income countries were to reduce their average consumption (or in-
come) to 20,000. The drop of 20,700 (viz. 40,700 – 20,000) international
dollars per person in a population of 1.4 billion adds up to a total of 31 tril-
lion international dollars. Other things equal, world income would then be
79 (viz. 110 – 31) trillion international dollars, a gure not far above the 70
trillion international dollars we obtained (Section 9) as a crude estimate
of sustainable global income under present-day technologies and social
institutions.
But problems abound. According to the projections in UNPD (2017),
world population will increase from the current 7.4 billion to 11.2 billion
in 2100. More than three-quarters of that increase is projected to be in sub-
Saharan Africa, from today’s approximately 1 billion to 4 billion. (Figure 2
presents the UN’s latest projections for regional populations up to the year
2100.) Per capita income in sub-Saharan Africa is currently 3,500 interna-
tional dollars. Comprising a little over 13 percent of the world’s population,
the region represents a bit in excess of 3 percent of the world economy.
So, sub-Saharan Africa cannot remotely be held responsible for the global
AISHA DASGUPTA /PARTHA DASGUPTA 431
FIGURE 2 Total population by region, 2015–2100
0
2
4
6
8
10
12
2015 2025 2035 2045 2055 2065 2075 20852095
Billions
Africa
Asia
Europe
Latin America and
Caribbean
Northern America
Oceania
SOURCE: UNPD 2017.
environmental problems we face today. But to raise incomes there even to
the current global average income (15,000 international dollars) in the face
of a 3-billion rise in numbers would require an increase in the region’s an-
nual output from 3.5 trillion dollars to 60 trillion dollars. That rise, assuming
it is possible, would have severe consequences for the region’s ecology, con-
tributing to further societal conicts there and to greater attempts by people
to move both within the region and out of it. It is not difcult to imagine
the international tensions that attempted movements on such a scale would
give rise to. The SDGs are largely silent on population, yet it is inconceivable
that they can be met without addressing the subject.40 Goal 13, for exam-
ple, recognizes that restricting the increase in mean global temperature to
2°C will require urgent collective action; but there is no acknowledgment
that the target is unlikely to be met unless population growth is reduced
substantially (O’Neill et al. 2010). The recent Paris Agreement on climate
change also made no mention of population.
432 SOCIALLY EMBEDDED PREFERENCES
If family planning programs were intensied to meet unmet need ev-
erywhere in Africa, population there would be some 1 billion smaller in
2100 than is currently projected by UNPD (2015).41 That in itself would
be a substantial gain for people in the region, but it would not be nearly
enough. We have argued that family planning is undervalued. Greater
investment in the service, bringing it into alliance with other social pro-
grams, could be expected to reduce the population projections further.
That fertility preference structures are socially embedded (whether by
conformity or competition, as in the wealth-in-people thesis) offers hope to
people in sub-Saharan Africa that population growth there can be stemmed
without much personal cost to them. That embeddedness also offers hope to
people everywhere that the environmental demands of the 1.4 billion peo-
ple in high-income countries can be reduced without too much personal
cost to people there. For if relative consumption matters, a uniform reduc-
tion in consumption among all should be expected to prove not too costly
to people. The population–consumption–environment nexus is one area of
the human experience where the cost of necessary social change is probably
much less than is feared by social scientists.
Notes
The views expressed in this essay are entirely
those of the authors and do not necessar-
ily reect the views of the United Nations.
For their helpful comments on a previous
draft, we are grateful to John Cleland, Rachel
Friedman, and Robert Solow.
1 The term natural capital is now in rou-
tine use among ecologists and economists to
remind us that Nature is a capital asset with
both intrinsic and use value. In what follows
we use the terms nature, natural capital, and
the natural environment synonymously. The
inuence of human numbers on the natu-
ral environment is again being noted in de-
mographic writings. See, for example, Bird-
sall, Kelley, and Sinding (2001), Bryant et al.
(2009), and Jiang and Hardee (2011).
2 The latter index was proposed by
UNDP (1990) and has been revised and up-
dated by the organization ever since.
3 For extended discussions on the place
of Nature in the lives of the world’s poor, see
Dasgupta (1993, 2007, 2010).
4 By providing access to subsidized con-
traceptive commodities and services, fam-
ily planning programs were successful in
accelerating fertility declines in Asia and
Latin America in the 1960s–1980s. One ra-
tionale for vigorously expanding the con-
tent and reach of such programs today lies
in the 189 million married/in-union women
of reproductive age in the developing world
(41 million in sub-Saharan Africa) who
have an unmet need for modern meth-
ods of contraception (UNPD 2016). In addi-
tion to reducing unintended births, contra-
ceptive use among women enhances their
own health and that of their children by
spacing births. And yet family planning re-
mains a neglected feature of public pol-
icy. Currently less than 1 percent of over-
seas development assistance is awarded to
it. Moreover, developing countries relegate
family planning expenditures to minor gov-
ernment departments. Despite evidence that
family planning reduces poverty, the World
Bank does not have family planning at its
core.
5 The binary classication of rights cor-
responds to Isaiah Berlin’s classication of
freedom into positive and negative categories
(Berlin 1959).
AISHA DASGUPTA /PARTHA DASGUPTA 433
6 Kumar and Hardee (2015) offer a use-
ful manual for family planning programs
based on the protection and promotion of re-
productive rights. Rights had been deployed
as an ethical category in discussions on fam-
ily planning and reproductive health prior to
the 1994 International Conference on Popu-
lation and Development. Hardee et al. (2014)
provide an account of that history as well as a
framework for achieving the goals of FP2020.
Cottingham, Germaine, and Hunt (2012) of-
fer an account of the power of the language
of rights in encouraging governments and in-
ternational agencies to provide the resources
needed to meet women’s unmet need for
family planning and reproductive health
facilities (see Section 5).
7 Brock (2010) contains an interest-
ing discussion of possible clashes between
parental rights and societal interests and how
societies variously resolve them. But he was
not concerned with the clash that is embod-
ied in environmental externalities. The ten-
sion between reproductive rights and sus-
tainable development has been commented
upon recently (e.g. Hardee 2014; Newman
et al. 2014), but it would appear not to have
inuenced development thinking.
8 World Bank (2012) reported that in
2010 the proportion of people who com-
pleted primary education was 96 percent in
India, 67 percent in Pakistan, and 65 per-
cent in Bangladesh. Total fertility rates (TFRs)
in those countries were 2.6, 3.4, and 2.2. It
should also be noted that in Bangladesh non-
governmental organizations at work on so-
cial matters have a far more extensive reach
than in India and Pakistan. Reproductive
behavior is not mono-causal.
9 Nudge theory advocates a weak ver-
sion of that idea. See Thaler and Sunstein
(2008).
10 Sen (1982) likens the emission of
persistent pollutants to torturing future peo-
ple. The clash between reproductive rights
and adverse environmental externalities al-
lied to new births is at its most striking under
his reading.
11 Writing about West Africa, Fortes
(1978, pp. 125–6) said “a person does not
feel he has fullled his destiny until he or she
not only becomes a parent but has grandchil-
dren. … [Parenthood] is also a fullment of
fundamental kinship, religious and political
obligations, and represents a commitment
by parents to transmit the cultural heritage
of the community.… Ancestry, as juridically
rather than biologically dened, is the pri-
mary criterion …for the allocation of eco-
nomic, political, and religious status.”
12 Between 1965 and 2015 the infant
mortality rate in sub-Saharan Africa declined
from about 150 deaths per 1,000 live births to
around 60 per 1,000.
13 For theoretical models that speak
to the mutual determination, see Das-
gupta (1993, 2000), Brander and Tay-
lor (1998), Harford (1998), Dasgupta and
Ehrlich (2013), and Bohn and Stuart (2015).
The mutual determination does not neces-
sitate a demographic trap, but it may lead
to one. See in particular Dasgupta (2000,
Appendix).
14 To see that there are no externali-
ties if the shares were the same, suppose cis
thecostofrearingachildandNis the num-
ber of couples within a kinship. Assume that
each child makes available yunits of output
to the entire kinship, which is then shared
equally among all couples in their old age.
Suppose also that the cost of rearing each
child is shared equally by all couples. Let n*
be the number of children each couple other
than the one under study chooses to have. If
nis the number of children this couple pro-
duces, they would incur the resource cost C
=[nc+(N–1)n*c]/N, and eventually the cou-
ple would receive an income from the next
generation equaling Y=[ny+(N–1)n*y]/N.
Denote the couple’s aggregate utility func-
tion by the form U(Y)–K(C), where both U(.)
and K(.) are increasing and strictly concave
functions. Letting nbe a continuous variable
for simplicity, it is easy to conrm that the
couple in question will choose the value of n
at which ydU(Y)/dY=cdK(C)/dC. The choice
sustains a social equilibrium when n=n*. It
is easy to check that this is also the condition
that is met in a society where there is no re-
productive free-riding. It follows that there is
free-riding if the parents’ share of the bene-
ts from having children exceeds their share
of the costs.
434 SOCIALLY EMBEDDED PREFERENCES
15 In an early review of fertility inten-
tions, Cochrane and Farid (1989) noted that
both the urban and rural and the educated
and uneducated in sub-Saharan Africa have
more, and want more, children than their
counterparts in other less-developed regions.
Even young women expressed a desire for an
average of 2.6 more children than women
in the Middle East, 2.8 more than women
in North Africa, and 3.6 to 3.7 more than
women in Latin America and Asia. Updated
versions of these gures are available, but
we are presenting data from the mid-1980s
because the income gap between Africa and
the rest of the developing world was smaller
at that time than it is now.
African society’s exceptionalism has been
much written about. See in addition Goody
(1976), Bledsoe and Pison (1994), Bon-
gaarts (2011), and Bongaarts and Casterline
(2013). But changes have been observed, at
least in East Africa. Fostering is declining,
land registration is increasing, and urbaniza-
tion is eroding pronatal institutions. Whether
those changes will markedly inuence fertil-
ity rates in the near future is unclear. And de-
lay matters to Africa’s future prospects (Sec-
tion 11). We are grateful to John Cleland for
helpful discussions on this.
16 Formally, we are studying Nash equi-
libria in a coordination game (see Dasgupta
1993, 2000; Kohler 2000). It can be shown
that the social equilibrium in which each
household has 4 children (n2) is unstable. It
would take us far aeld to explain why, but
see Dasgupta (2002) for the reason.
17 Farooq, Ekanem, and Ojelade (1987)
is an early study of the phenomenon in West
Africa. Lutz, Butz, and KC (2014) is a collec-
tion of essays on the effect of education on
fertility behavior. Interactions between the
elite and the general public can be a vehicle
by which fertility behavior among the poor
changes.
18 The media are increasingly used to
such an end. For example, Development
Media International runs media campaigns
aimed at changing behavior.
19 For a wide-ranging discussion of the
role of societal norms in fertility behavior, see
Bongaarts and Watkins (1996).
20 Diffusion processes had been studied
long before, in connection with technology
adoption. In a classic paper, Griliches (1957)
conducted an empirical study of the spread of
hybrid corn in the US. In his model, farmers
observed the successful adoption of new va-
rieties before adopting them themselves. The
process gave rise to the now-familiar logis-
tic pattern of adoption. On the effect on re-
productive behavior of the diffusion of ideas
brought about by family planning programs,
see Babalola, Folda, and Babayora (2008)
and Krenn et al. (2014).
21 Casterline and Sinding (2000) dis-
cuss ways in which the measure of unmet
need can be used to inform family planning
policies.
22 Because people’s preferences differ,
we should expect the responses to differ
but discover that each individual’s preferred
number of children is an increasing function
of n. That nding would reveal socially em-
bedded preferences.
23 Moral philosophers would argue that
the evaluation of family planning programs
should include the quality of lives that will
not be lived on account of the programs. We
avoid those further considerations by assum-
ing that thoughtful parents reach their fer-
tility desires by taking into account the po-
tential well-being of their offspring and, by
recursion, the well-being of their dynasty.
24 αis not a constant and is most likely
a decreasing function of K.
25 A tractable form of F(K), in wide use
among ecologists for a variety of ecosystems,
is quadratic:
F(K)=rK(1–K/K*),
where rand K* are positive constants. In this
equation ris the intrinsic growth rate of K
(because rat small values of Kis the percent-
age rate of growth of K)andK*isEarth’scar-
rying capacity (because F(K*) =0).
The view that the biosphere is a renew-
able natural resource covers pollution as well
(e.g., contemporary carbon emissions into
the atmosphere). Pollutants are the reverse
of natural resources. One way to conceptual-
ize pollution is to view it as the depreciation
AISHA DASGUPTA /PARTHA DASGUPTA 435
of capital assets. Acid rains damage forests;
carbon emissions into the atmosphere trap
heat; industrial seepage and discharge re-
duce water quality in streams and under-
ground reservoirs; bers and plastics dam-
age life in the oceans; sulfur emissions cor-
rode structures and harm human health; and
so on. The damage inicted on each type
of asset (buildings, forests, the atmosphere,
ocean sheries, human health) should be
interpreted as depreciation. For natural
resources, depreciation amounts to the dif-
ference between the aggregate rate at which
they are harvested and their natural regen-
erative rate; for pollutants the depreciation
they inict on natural resources is the dif-
ference between the rate at which pollu-
tants are discharged into the resource base
and the rate at which the resource base is
able to degrade it. The task in either case
is to estimate those depreciations. It fol-
lows that there is no reason to distinguish
the analytical structure of resource manage-
ment problems from pollution management
problems. Roughly speaking, “resources” are
“goods,” while “pollutants” (the degrader of
resources) are “bads.” Pollution is the reverse
of conservation.
26 Carbon and sulfur dioxide emissions
rose by a factor of more than 10.
27 The term Anthropocene was popu-
larized by Crutzen and Stoermer (2000) to
mark a new epoch that began with the In-
dustrial Revolution some 250 years ago.
28 The “hockey stick” graph refers to
time series of carbon concentration in the at-
mosphere over the past 500 years. The vari-
able grew gently from the late eighteenth
century until the twentieth century, when
it displayed a sharp increase. The Anthro-
pocene Working Group has recently pro-
posed that the immediate postwar years
should be regarded as the start of the Anthro-
pocene. See Vosen (2016).
29 Qis also called the notional price
and, more often, shadow price. The litera-
ture on valuing natural capital is vast (see
for example, Freeman 2003; Haque, Murty,
and Shyamsundar 2011). A number of stud-
ies have estimated shadow prices of specic
types of natural capital at the local level
(water, air quality, woodlands, mangroves,
coral reefs), but economic demographers es-
timating the value of family planning pro-
grams at the local level have not made use of
them.
In recent years estimating costs of car-
bon emissions for the global climate has been
a major research topic. The basic idea is to
estimate the net present value of the im-
pact over the next 100 years (or more) on,
for example, agriculture from changes to the
global climate that are traceable to carbon
emissions. That is Qwhen restricted to the
stock of carbon in the atmosphere. The net
present value has been found to be negative
(meaning that global climate change is ex-
pected to hurt the world economy; that is,
the notional price of carbon is negative) and
has been estimated using a range of plausi-
ble gures for the rates at which future costs
and benets are to be discounted. See Moore
and Diaz (2015), who arrive at a gure of 220
US dollars per ton of carbon emitted into the
atmosphere. In contrast, the US government
uses a gure of 37 dollars per ton. The wide
difference in the estimates reects differences
in assumptions regarding the effect of carbon
emissions on the global climate and in turn
the effect of changes in the global climate on
the fruits of human activities.
Bohn and Stuart (2015) offer estimates
of the social cost of carbon emissions owing
to a new birth (that is QK,butwhereK
is restricted to carbon concentration and Q
is the shadow price of carbon in the atmo-
sphere). In contrast, the literature contains
next to nothing on the valuation of changes
that humanity is inicting on the oceans and
the biomass they harbor. We do not know Q
for the biosphere.
30 For pioneering work on the idea of
ecological footprints, see Rees and Wack-
ernagel (1994) and Rees (2001, 2006).
See also Kitzes et al. (2008). Wakernagel,
who founded the Global Footprint Network
(www.footprintnetwork.org/public), was a
lead author of WWF (2008).
31 The Daily–Ehrlich–Ehrlich study was
based on the assumption that the sources of
energy will continue to be fossil fuels. To-
day there is hope that energy in due course
will altogether be obtained from renewable
436 SOCIALLY EMBEDDED PREFERENCES
resources. Meanwhile Kwill have been fur-
ther depleted. And climate change is not the
only source of stress to the Earth system. Co-
hen (1995) collated a wide range of estimates
that had been published in the past century
of Earth’s capacity to support human num-
bers and their demands.
32 The literature on reported happiness
is huge. See Helliwell, Layard, and Sachs
(2013) for a ne review of the large-scale sur-
veys that ask people to report their feelings
and emotions and collate their responses.
33 Layard (2011, pp. 32–35) reports the
nding and commends it. A number of ex-
planations can be given for the nding, one
being that what matters most to a house-
hold beyond a certain level of income is its
income relative to the average income in its
peer group. Veblen (1899 [1925]) based his
theory of the leisure class on this particular
psychology of consumption. Veblen’s obser-
vation on human psychology found a telling
expression in a remark attributed to a Garry
Feldman of Stamford, Connecticut, one of
the wealthiest towns in the US: “I might be
in the top one percent, but I feel that I am in
the bottom third of the people I know” (The
Guardian, 16 February 2013).
Another explanation for happiness satu-
ration bases itself on the idea that people are
conformists on styles of living. The problem
is not that either explanation is implausible
(they are both all too believable), but that
either dominates all other factors affecting
the demand for goods and services beyond
20,000 international dollars. We use the g-
ure only for illustration.
34 10,000 international dollars is the
per capita income in contemporary Albania
and Indonesia.
35 See for example the regular com-
mentaries in The Economist.Theabsolute
poverty line is currently taken by the World
Bank to be 1.90 international dollars a
day. It is an adjustment to the dollar-a-day
gure that was introduced by the Bank in the
1980s.
36 To conrm this, suppose population
size is N; people are indexed by i(=1, 2, …,
N); and yiis person i’s income. Let eibe i’s
demand for ecological services. A simple way
to formulate the assumed relationship be-
tween income and biomass consumption is
ei=Ayiπ,
where 0 <π<1andA>0 are constants.
Global demand for ecological services is then
E=
i
ei=A
i
yπ
i,
where
i
denotes summation over i.
Suppose there is an increase in all in-
comes by g, expressed in percentages. Then
the global demand for ecological services (E*)
would be
E*=(1+g)πE<(1+g)E.
37 To see why, we use the notation
introduced in the previous endnote and con-
sider the extreme case where there is com-
plete equality of incomes following the redis-
tribution. For vividness, label people so that
y1<…<yi<…<yN. Write the mean global
income as y*. Then y∗=iyi/N. Suppose
g=0 (global GDP does not change). By as-
sumption 0 <π<1. That means NA(y∗)π>
Aiyπ
i.ButNA(y*)πis the global de-
mand for ecological services under complete
equality.
38 To conrm, one could use the model
in endnote 37, but assume π>1.
39 Landes (1998) is a classic on the
subject.
40 Starbird, Norton, and Marcus (2016)
contains a good discussion of this.
41 We are grateful to John Bongaarts for
correspondence on this.
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