ELECTORAL SYSTEMS-Party System Effects on Electoral Rules

Abstract

A long tradition of empirical studies has focused on the consequences of electoral systems on party systems. A number of contributions have turned this relationship upside down by postulating that it is the parties that choose electoral systems and manipulate the rules of elections. The most remote shaping of innovative electoral rules, the choice of electoral systems in new democracies, and further electoral reforms in well-established regimes can be explained on the basis of political parties' relative strength, expectations, and strategic decisions. In a broader institutional context, political parties can also trade off electoral systems with choices and changes of other institutional rules.

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Party System Effects on Electoral Rules
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Abstract and Keywords
A long tradition of empirical studies has focused on the consequences of electoral
systems on party systems. A number of contributions have turned this relationship upside
down by postulating that it is the parties that choose electoral systems and manipulate
the rules of elections. The most remote shaping of innovative electoral rules, the choice of
electoral systems in new democracies, and further electoral reforms in well-established
regimes can be explained on the basis of political parties’ relative strength, expectations,
and strategic decisions. In a broader institutional context, political parties can also trade
off electoral systems with choices and changes of other institutional rules.
Keywords: political parties, electoral system choice, Duverger’s propositions, micromega rule, plurality rule,
multimember districts, proportional representation
Introduction
Political parties and electoral systems have been analyzed both as a cause and as a
consequence of each other. First, a long tradition of empirical studies focused on the
consequences of electoral systems on party systems. Most prominently, Maurice Duverger
postulated that “old” political parties were created internally in elected (and also in
nonelected) assemblies and parliamentary groups (Duverger 1951). Empirical analyses of
party systems, which typically focus on democratic regimes from the mid-twentieth
century on, usually assume that political parties derive from given elections and electoral
systems that can be taken as the independent variable in the explanatory framework.
A number of contributions have turned this relationship upside down by postulating that
it is the parties that choose electoral systems and manipulate the rules of elections. The
origins of the invention and adoption of different electoral rules and procedures,
Party System Effects on Electoral Rules
Josep M. Colomer
The Oxford Handbook of Electoral Systems
Edited by Erik Herron, Robert Pekkanen, and Matthew Søberg Shugart
Subject: Political Science, Parties and Bureaucracy, Political Institutions
Online Publication Date: Apr 2017 DOI: 10.1093/oxfordhb/9780190258658.013.16
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especially during the nineteenth and early twentieth centuries, can be found in the
incentives created by political party competition. Further electoral reforms, as well as the
choice of electoral systems in new democracies, can also be explained on the basis of
political parties’ relative strength, expectations, and strategic decisions. With this
approach, it is the political parties that can be taken as given and work as the
independent variable to explain the emergence of different electoral rules. It can also be
hypothesized, nevertheless, that changes in the party system—which is the focus of this
chapter—tend to have significant effects on the electoral systems in the long term, while
changes in electoral rules may have short-term effects on political party competition.
This chapter reviews, first, the most remote origins of political parties and how they
began to shape innovative electoral rules; second, how different political party
configurations influence the choice, permanence, or change of electoral rules; and third,
the tradeoffs that political parties consider between electoral systems and other
institutional rules.
Origins of Parties and Electoral Systems
To understand the origins of political parties and how they shaped innovative electoral
rules, we must pay attention to the role of traditional elections in local settings. A very
simple type of electoral system was used widely in local and national assemblies in
predemocratic or early democratic periods before and during the nineteenth century. The
essential elements of this type of electoral system are multiseat districts, open ballot
(permitting the voter to vote for a number of individual candidates equal or lower than
the seats to be filled), and plurality or majority rule.
This combination of rules has been widely used, especially in relatively simple elections
with rather homogeneous electorates, and particularly at the beginning of modern
suffrage regulations and for small-size local governments. It is still a common type of
procedure for local or municipal elections in many countries, as well as in many meetings
and assemblies of modern housing condominiums, neighborhood associations, school and
university boards and delegates, professional organizations, corporation boards, and
students’ and workers’ unions. In these, as well as in many of the traditional communities
just mentioned, individual representation is well suited to contexts of high economic and
cultural homogeneity in which it is relatively easy to identify common interests and
priority public goods to be provided by the elect.
This set of electoral rules appears indeed as almost “natural” and “spontaneous” to many
communities when they have to choose a procedure for collective decision making based

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on votes, especially because it permits a consensual representation of the community.
Such a simple electoral system is able to produce satisfactory and acceptable citizens’
representation. But it also creates incentives for self-interested, would-be political leaders
to coordinate on “factional” candidacies or voting coalitions—in a word, “parties.” Under
that system, forming or joining a “party” may increase the prospects of winning
additional votes and seats. “Party” is thus defined here in a minimalist way that is not
substantially different from traditional meanings of “faction” in early periods of voting
and elections.
Under the previously identified set of rules, factions or parties tend to induce “voting in
bloc” for a list of candidates, which may change election results radically. Once party
candidacies are presented, it is not necessary that all or most voters follow the advice of
factional leaders to vote for all of and only the members of a list of candidates to attain a
party sweep. It may be sufficient that a few people do it, since, even if they are few, they
can make a difference, especially under simple plurality rule where no specific threshold
of votes is required to win. Note that, in historical terms, voting “in bloc” was not an
institutionally induced behavior, but a party-strategy-induced behavior.
In some crucial cases, it was largely as a consequence of this type of experience that
different political leaders, candidates, activists, and politically motivated scholars began
to search for alternative, less intuitive, or “spontaneous” electoral rules able to reduce
single-party sweeps and exclusionary victories. This new period began to develop by the
mid-nineteenth century. It can be held that from that moment on, it was the previously
existing political parties that chose, manipulated, and promoted the invention of new
electoral rules, including the Australian ballot, single-seat districts, limited ballot, and
proportional representation rules, rather than the other way around.
Virtually all the new electoral rules and procedures that were created since the
nineteenth century can be understood as innovative variations of the previous, simple,
“originating” system, which can be called “originating” precisely for this reason. The new
electoral systems can be classified in three groups, depending on whether they changed
the district magnitude, the ballot, or the rule.
The first group implied a change of the district magnitude from multiseat to single-seat
districts, keeping both individual-candidate voting and majoritarian rules. With smaller
single-seat districts, a candidate that would have been defeated by a party sweep in a
multiseat district with plurality rule may be elected. Thus, this system tends to produce
more varied representation than multiseat districts with voting in bloc, although less
varied than multiseat districts with open ballot.
The second group of new electoral rules implied new forms of ballot favoring individual-
candidate voting despite the existence of party candidacies, while maintaining the other

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two essential elements of the traditional system: multiseat districts and majoritarian
rules. In particular, by limited vote, one party can sweep as many seats as the voter has
votes, but it is likely that the rest of the seats will be won by candidates of different
political affiliation.
Finally, the third group of new electoral rules implied the introduction of proportional
representation formulas, which permit the maintenance of multimember districts and in
some variants also open or individual-candidate ballot. Single-transferable vote, double
vote, preferential voting, and open ballots make individual-candidate voting compatible
with proportional representation (Colomer 2007).
This discussion can clarify the conundrum of the relationship between party systems and
electoral systems, as if they were related like the chicken and the egg. Actually, biologists
have an answer for the latter inquiry: in the beginning was an egg, but a very simple one,
not a chicken’s egg. Analogously, we can say that first, there were elections, but with very
simple rules, not party elections. Once the parties were formed, they delivered more
complex and varied “eggs,” or electoral systems.
The Parties’ Strategic Choices of Electoral
Systems
This early history can be expanded for the further period since the late nineteenth
century. In contrast to the basic assumption in the old tradition of electoral studies
referred to earlier, it is the number of parties that can explain the choice of new electoral
systems, in particular regarding the introduction of proportional representation rules,
rather than the other way around.
In fact, Maurice Duverger himself briefly noted that “the first effect of proportionality is
to maintain an already existing multiplicity” (Duverger, 1950, 1951, 344). In a review of
Duverger, John G. Grumm (1958, 375) held that “the generally-held conclusions regarding
the causal relationships between electoral systems and party systems might well be
revised…. It may be more accurate to conclude that proportional representation is a
result rather than a cause of the party system in a given country.” Leslie Lipson (1964,
343) developed a historical narrative from the premise that “chronologically, as well as
logically, the party system is prior to the electoral system.” Stein Rokkan noted:
In most cases it makes little sense to treat electoral systems as independent
variables and party systems as dependent. The party strategists will generally

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have decisive influence on electoral legislation and opt for the systems of
aggregation most likely to consolidate their position, whether through increases in
their representation, through the strengthening of the preferred alliances, or
through safeguards against splinter movements.”
(Rokkan 1968; see also Lipset and Rokkan 1967)
Arend Lijphart and Bernard Grofman (1984) explored the factors for the “not highly
probable, but possible” changes and choices in electoral systems. Rein Taagepera (2003,
5) more recently also suggested a “causality following in the reverse direction, from the
number of parties towards electoral rules.”
Some recent contributions in this approach compare not only different countries using
different rules, as is customary in the previously cited works, but also every single
country before and after the introduction of new electoral rules. By putting “the
Duverger’s laws upside down,” Josep Colomer (2004, 2005) showed how previously
existing political party configurations dominated by a few parties tend to establish
majority-rule electoral systems, while multiparty systems already existed before the
introduction of proportional representation.
The emphasis on this line of causality does not deny that existing electoral systems offer
different positive and negative incentives for the creation and endurance of political
parties. Precisely because electoral systems can have important consequences on shaping
the party system, it can be supposed that they are chosen by already existing political
actors in their own interest. Accordingly, it can be expected that, in general, electoral
systems will crystallize, consolidate, or reinforce previously existing political party
configurations, rather than (by themselves) generate new party systems.
We know that electoral systems based on the majority principle, which tend to produce a
single, absolute winner and subsequent absolute losers, are riskier for nondominant
actors than those using rules of proportional representation—a principle that was forged
to create multiple partial winners and far fewer total losers than majority rules. In
general, the “Micromega rule” can be postulated: the large will prefer the small and the
small will prefer the large. A few large parties will prefer small assemblies, small district
magnitudes (the smallest being one), and small quotas of votes for allocating seats (the
smallest being simple plurality, which does not require any specific threshold), to exclude
others from competition. Likewise, multiple small parties will prefer large assemblies,
large district magnitudes, and large quotas (like those of proportional representation),
which are able to include them within the legislature.
Changing electoral rules can be a rational strategy for likely losers or threatened winners
if the expected advantages of alternative rules surpass those of playing by the existing

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rules minus the costs of change. In particular, an alteration of the electoral system can be
more successfully promoted by parties with high decision, negotiation, or pressure power
under the existing institutional framework. This makes incumbent rulers submitted to
credible threats by new or growing opposition parties likely candidates to undertake
processes of institutional change.
Thus, it can be expected that in situations in which a single party or two parties
alternating or sharing power are institutionally dominant and expect to obtain or
maintain most voters’ support, restrictive rules based on majority requirements will be
chosen or maintained. Since this type of electoral rule tends to produce a single absolute
winner, it can give the larger parties more opportunities to remain as winners and retain
control—as can happen, in particular, during long processes of gradually broadening
suffrage rights and democratization, giving the incumbent rulers significant opportunities
to define the rules of the game.
In contrast, it may be that no single group of voters and leaders, including the incumbent
ruling party, is sufficiently sure about its support and the corresponding electoral
prospects in future contests. In other words, there can be uncertainty regarding the
different groups’ relative strength or it can be clear that electoral support is going to be
widely distributed among several small parties. Here changes in favor of less risky, more
inclusive electoral rules, such as mixed or proportional representation electoral systems,
are more likely to be promoted and established by the currently powerful actors in their
own interest. This tends to be the development preferred by new or newly growing
parties in opposition to traditional rulers, including, in particular, multiparty opposition
movements against an authoritarian regime. But it can also be favored by threatened
incumbent rulers to minimize their possible losses (Colomer 2004, 2005).
These analyses have been developed for the introduction of proportional formulas for the
elections of parliaments. Analogous strategies have been observed more recently for the
choice and change of rules to elect the president in separation-of-power regimes. In Latin
America, it has been observed that while dominant and large parties are likely to choose
plurality rule and concurrent elections, small parties are likely to choose nonconcurrent
elections with majority rule with a second-round runoff, which permit multiparty
competition. It has also argued that military rulers and military–civilian coalitions in
processes of redemocratization, as they may feel threatened by newly emerging party
configurations, tend to follow the logic of electoral choice of small parties (Negretto
2006).
When dealing with presidential elections, shifting partisan political fortunes have also
been placed at the center of analysis. Changes in the rules of the electoral game tend to
reflect the political self-interest of dominant political parties as defined in relation to

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mounting electoral uncertainty. The impact of electoral reforms on party system change,
in contrast, appears to be less consistent with the expectations derived from the more
traditional literature. In particular, party system change in Latin America has generated
institutional change more predictably than vice versa (Remmer 2008).
Additional caveats can be introduced. If the incumbent rulers are still sufficiently
powerful, they may prefer mixed-member systems, rather than openly proportional rules,
in the aim of reducing political fragmentation and limiting the potential for new entrants
to the party system (Shugart and Wattenberg 2003; Reilly 2007). Also, the incumbents’
willingness to introduce electoral system change may derive not only from a serious
threat to their dominance but also from their loss of control of the situation or some
internal division of interests among its members. The rules for changing the rules also
matter. If the incumbent government can change the electoral law without seeking a
broader agreement, there is greater likelihood that partisan self-interest will dominate.
On the other hand, change may be deterred by high barriers to change, such as the
constitutionalization of the electoral system or the requirement of a parliamentary
supermajority or a popular referendum for its change (Gallagher 2005; Katz 2005).
Electoral Behavior and Institutional Choice
By reassuming the two approaches referred to previously, it can be postulated that self-
interested parties competing in elections can develop two strategies at the same time:
behavioral and institutional. In the behavioral field, the basic decision is to create or not
an electoral partisan candidacy. More specifically, to create a new partisan candidacy
might imply either a new effort of collective action or splitting from a previously existing
party, while not to create a new candidacy may mean entering a previously existing party,
forming an electoral coalition, or merging with a rival party. In the institutional field, the
decision is to promote or not a change in the electoral system, the two basic polar
alternatives being either majoritarian or proportional representation rules.
Given the electoral system, the actors’ relevant strategy lies mainly in the behavioral
field. Under the “originating” system, there were incentives for self-interested actors to
create new partisan candidacies. If there is a majoritarian electoral system, the rational
strategy is not to create a party. Instead, it makes sense to coordinate efforts with other
would-be leaders and groups to form only a few large parties or coalitions in the system
(typically two), each of them able to compete for offices with a reasonable expectation of
success. By contrast, if the existing electoral system is based on the principle of
proportional representation and is inclusive enough to permit representation of small
parties, rational actors may choose either coordination or running on their own

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candidacies, in the expectation that in both cases they will obtain the corresponding
office rewards.
However, emerging parties may produce unwelcomed sweeps, coordination may fail, and,
especially under majoritarian systems, lack of coordination may produce defeats and no
representation for candidates, groups, and parties with some significant, real or
potential, support among voters. In these cases, the alternative strategic field—the choice
of electoral institutions—becomes relevant. Parties unable to coordinate themselves into
a small number of large candidacies will tend to prefer electoral systems able to reduce
the risks of competing by giving all participants higher opportunities to obtain or share
power. Two-party configurations are likely to establish or maintain majoritarian electoral
systems, while multiple-party configurations will tend to mean that political actors choose
systems with proportional representation rules. Also, majoritarian electoral systems tend
to restrict effective competition to two large parties, while proportional representation
permits multiple parties to succeed.
This discussion brings together “institutional theories,” which include those about the
political consequences of electoral systems, and “theories of institutions,” in this case
regarding the choice and change of electoral systems. A “behavioral-institutional
equilibrium” can be produced by actors with the ability both to choose behavioral
strategies (such as a party, candidacy, or coalition formation deciding on electoral
platforms or policy positions) and to choose institutions regulating and rewarding those
behaviors.
In the long term, two polar behavioral-institutional equilibria can be conceived. In one,
political actors coordinate into two electoral parties or candidacies under majoritarian
electoral rules. In another, multiple parties compete separately under proportional
representation electoral rules. Either of the two results can be relatively stable and
durable, but there is no deterministic relationship able to predict which one is going to
prevail (there are also other intermediate pairs of consistent behavioral and institutional
alternatives, including imperfect two-party systems, mixed electoral systems, and so on).
In this approach the presumed line of causality is double. Two-party configurations tend
to maintain or choose majoritarian rules, while multiparty systems tend to establish or
confirm proportional representation rules. In turn, majoritarian rules induce the
consolidation of two large parties, while proportional representation confirms the
potential for the development of multiple parties.
A crucial point is that coordination failures can be relatively more frequent under
majoritarian electoral systems than under proportional rules, especially for the costs of
information transmission, bargaining, and implementation of agreements among
previously separate organizations, as well as the cost of inducing strategic votes in favor

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of the larger candidacies. With coordination failures, people will waste significant
amounts of votes, and voters’ dissatisfaction with the real working of the electoral system
may increase. Large numbers of losing politicians are also likely to use voters’
dissatisfaction and their own exclusion, defeat, or underrepresentation to develop
political pressures in favor of changing to more proportional electoral rules.
In contrast, coordination failures, properly speaking, should not exist under conditions of
flawless proportional representation. Even if the number of candidacies increases, each
of them can expect to obtain about the same proportion of seats that they would have
obtained by forming part of more encompassing candidacies. In reality, coordination
failures are relevant under proportional systems to the extent that they are not properly
proportional, particularly when small assembly sizes and small district magnitudes are
used.
An important implication is that, in the long term, we should expect that most electoral
system changes should move away from majoritarian formulas and in favor of systems
using rules of proportional representation. Reverse changes, from proportional toward
more majoritarian rules, may be the bet of some potentially dominant, growing, or daring
party. But they can imply high risks for a partial winner to be transformed into a total
loser, if its optimistic electoral expectations are not confirmed. This occurrence may be
more frequent when actors are risk prone or badly informed about electoral systems. In a
historical perspective, there have been increasing numbers and proportions of electoral
systems using proportional representation formulas rather than majoritarian rules.
Party System Configurations
Several discussions of specific political party configurations in which we should expect
different types of electoral system change have been proposed. Stein Rokkan (1968)
analyzed the origins of proportional representation by taking inspiration from Karl
Braunias (1932), who distinguished two phases in the spread of proportional
representation electoral rules: the “minority protection” phase, before World War I, and
the “antisocialist” phase, in the years immediately after the armistice. This approach has
been further developed with a focus on the turn of the twentieth century by Boix (1999);
Blais, Dobrzynska, and Indridason (2005); and Cusack, Iversen, and Soskice (2007)
regarding Europe, and by Calvo (2009), Wills-Otero (2009), and Gamboa and Morales
(2015) for Latin America. Boix, in particular, analyzes the shift from the plurality/majority
rule to proportional representation as a result of the entry of new voters (assumed to be
left-wing voters) and a new party (socialist) at the turn of the twentieth century in the

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Western world. Heanalizes the shift from the plurality/majority rule to proportional
representation as a result of the entry of new voters.
Kenneth Benoit (2004, 2007) sketches a more general model of electoral system change
at political parties’ initiative. He assumes that the parties’ objective is to maximize their
share of seats. Benoit gives some real-life examples of electoral system change and
discusses some empirical implications of his model. He predicts that the electoral rule
will be changed when a coalition of parties, which have sufficient power to change the
rule, exists such that each party in the coalition would gain more seats under the new
rule.
In Colomer’s (2005) analysis, parties will be interested in replacing majoritarian rules
with more inclusive systems, typically proportional representation rules, if none of them
can be sure of winning by a majority. In other words, electoral system change from
majority rule to a more inclusive electoral system permitting representation of minorities
can be a rational choice if no party has 50 percent of popular votes, which is the
threshold guaranteeing representation under the former system. Configurations in which
one party has more than 50 percent of votes have values for the effective number of
parties of between 1 and 4, with an expected average at 2.5. Changes in favor of
proportional representation will not take place with values of the effective number of
parties below 2, for lack of powerful actors with an interest in such a change. Above four
effective parties, maintaining or establishing a majority-rule electoral system would be
highly risky for the incumbent largest party, and possibly not feasible either, due to
pressures for an alternative system supported by a majority of votes.
We mentioned that the elections held immediately after the adoption of proportional rules
tend to confirm, rather than increase, the previously existing multiparty configuration.
However, the new rules transform the share of each party in votes into fairer party seat
shares, thus making it more attractive for voters to give their support to new or emerging
political parties. As a consequence, the effective number of parties tends to increase in
the long term, thus creating further pressures in favor of maintaining proportional rules.
In further elaboration, Selim Ergun (2010) holds that for a change to occur, the
government should be formed by a coalition. He finds that a change is more likely to
occur when there is a larger number of parties and also when the spoils of office are
shared equally among the members in the governing coalition. These results are
extended to analyze partial reforms from a less proportional rule to a more proportional
one.
Ergun finds that a change can also occur when the effective number of parties is between
two and three. The crucial point is not necessarily the size of the largest party but the
difference between the parties. In the case of three parties, the largest party is always

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against a change and the smallest party always in favor, and thus the electoral system will
be changed depending on the size of the median-sized party. In a three-party
configuration, the second party in size will successfully promote proportional
representation if its size is sufficiently distant from the largest party size and, as a
consequence, it cannot guarantee leading a majority coalition with the third party under
majority rule.
Looking to the question from the other side, some authors have discussed the political
party conditions for establishing majority rule. Eunju Chi (2014) examines how party
competition led to electoral reforms in Taiwan. The two larger parties, driven by the goal
of maximizing the number of seats, formed a coalition and passed reform bills to change
the electoral system from a single nontransferable vote and multiseat district system to a
first-past-the-post mixed system. Konstantinos Matakos and Dimitrios Xefteris (2015)
identify more general, favorable conditions for introducing majority rule, such as the
expected vote share of the smaller parties, the high rents from a single-party government,
and sufficient uncertainty over the electoral outcome.
Further contributions include the examination of situations in which the party system is
weakly institutionalized and high levels of electoral volatility can be observed. For
relatively recent democracies, such as in Eastern Europe, these situations deter the
stabilization of electoral systems and make relevant actors prone to engage in reforms
(Bielasiak and Hulsey 2013). The role of actors other than parties, such as voters,
academics, and reform activists, has also been highlighted in specific cases (e.g., Renwick
2010; Leyenaar and Hazan 2011).
Institutional Tradeoffs
Political parties usually address the maintenance or change of electoral rules in the
broader context of the institutional system, thus developing tradeoffs with changes of
other institutional rules. Most significant rules to consider are the extension of suffrage
rights, the size or number of seats of the assembly, and the number of territorial
governments in a federal-like structure.
The extension of suffrage rights was usually perceived as a potential source of emergence
of new political parties than can challenge the status quo. The dominant parties in the
existing system were wary of expanding suffrage if no parallel institutional rules were
introduced to reduce the risk of being defeated and becoming noncompetitive parties in
the new system. That is why many successful processes of expansion of suffrage rights
were accompanied by reforms in the electoral rules.

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A case for reference is the United Kingdom, the oldest democracy still using plurality rule
in single-seat districts. Major change of electoral rules was prevented by avoiding the
sudden introduction of universal (male) suffrage and following a long process of gradual
enlargements of suffrage rights in the nineteenth and early twentieth century.
Requirements of wealth, property, income, or literacy for voting were safeguards against
a possible turnabout of the political and party system by the sudden irruption of new
mass voters. While the political system was dominated by alternations in government
between the Conservative and the Liberal Parties, the electoral system (at the time still
including a number of multimember districts by plurality rule) was not challenged.
It was the emergence of the new Labour Party, broadly supported by recently
enfranchised workers, at the beginning of the twentieth century that introduced demands
for proportional representation. Yet, when in the late 1920s the Labour leaders forecasted
a possible party victory under the existing electoral rules they turned against their own
former proposals for proportional representation. The new alternation between
Conservatives and Labourites since the end of the World War II had the effect of
converting the Liberals, which were excluded then from government, into the heralds of
electoral reform.
A different type of process could be observed in Germany and, even more clearly, in
northern European countries such as Sweden, Norway, and Finland. In these countries,
the sudden enfranchisement of a very large electorate was made compatible with
appreciable degrees of political stability by the introduction “from above” by the
incumbent rulers of new electoral systems favoring political pluralism. By the early
twentieth century, proportional representation or similar institutional “safeguards”
promoting multiparty politics were adopted. Governments were then able to rely on
parliamentary coalitions in which centrist and moderate parties were expected to play a
decisive role. In this way, the risk of instability and the threat of turnabouts were limited,
and incumbent voters and leaders enjoyed continued opportunities of being included in
government and maintaining a significant influence on the political process.
In these countries, suffrage rights were traded off with electoral rules. Proportional
representation was adopted as an institutional safeguard in place of the traditional
qualifications for voting rights. New electoral systems permitting multipartism were
conceived to be protective devices. The Conservatives, the Liberals, or the Agrarians
would become a minority, but they would not be expelled from the system as might be
risked with a majoritarian rule. The incumbent rulers took the initiative of introducing
universal suffrage “with guarantees” rather than witnessing their own defeat (Lewin
1989; Acemoglu and Robinson 2000; Colomer 2001; Ahmed 2013).

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Another institutional rule that can be traded off with changes of electoral rules is the
number of seats of the assembly. The total number of seats to be elected in a country may
enlarge or restrict the number of viable parties and, more generally, the degree of
inclusiveness of the political system. According to Rein Taagepera (2001, 2007), the
number of parties in parliament, P, is related to the number of seats in the average
electoral district, M, and the total number of seats in the assembly, S. In his notation
Taagepera’s focus on predicting the number of parties may suggest that the number of
parties is always a dependent variable of the basic elements of the electoral systems. But
his formula accepts two-direction lines of causality. It can indeed be turned the other way
around to present the electoral system as derived from the number of parties.
Specifically, M = P /S.
This formula shows that the number of previously existing parties (which is raised to the
fourth power) is more important than the size of the assembly to explain the choice of
electoral system (as operationalized by M). As long as the size of the assembly is not
manipulated, for a small country with a small assembly, just a few parties can be
sufficient to produce a change of electoral system in favor of proportional representation.
In contrast, for a large country and a large assembly, many parties would be necessary to
produce such a result—as reform activists in the United Kingdom, for instance, know very
well.
But we can also deduct from the previous formula that, for a similar number of parties, P,
the larger the country, and hence the larger the assembly, S, the smaller the expected
district magnitude, M, can be. Very large countries, precisely because they have large
assemblies, should be associated to small (single-seat) districts. For example, the
institutional designers in large India are likely to choose single-seat districts, while the
institutional designers in small Estonia are likely to choose multimember districts,
typically associated with proportional representation rules. Thus, we should usually see
large assemblies with small districts, and small assemblies with large districts.
The interest of this finding is that it is counterintuitive, since apparently small countries
should have more “simple” party configurations, so that they could work with simple
electoral systems with single-seat districts and majority rule in acceptable ways (actually
this tends to happen in very small and micro-countries with only a few dozen thousand
inhabitants in which only one or two significant parties emerge). But now we have an
answer to the very intriguing question of why some very large countries, including the
United States, in spite of the fact that large size is typically associated with high
heterogeneity, keep small single-seat districts and have not adopted proportional
representation. The answer may be that in large countries, such as Australia, Canada,
4

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France, India, the United Kingdom, and the United States, a large assembly can be
sufficiently inclusive, even if it is elected in small, single-seat districts. By contrast, in
small countries, including Belgium, Denmark, Estonia, Finland, the Netherlands, Norway,
Switzerland, and so many others, the size of the assembly is small and, as a consequence,
the development of multiple parties has favored more strongly the adoption of more
inclusive, large multimember districts with proportional representation rules.
The large size of a country and its assembly is also usually associated with a federal
structure. In fact, the electoral system can also be traded off with federalism, as a high
number of decentralized territorial governments can play an inclusive role of the variety
of the population in large countries and make proportional representation unnecessary,
as discussed in Colomer (2010). As always, the tradeoff is operated through human
collective action. If in a large country multiple territorial governments are established,
much political action will focus on those local institutions and it will be less likely that
multiple political parties will be formed at the countrywide level. As a consequence, there
will be less pressure to adopt a federal large assembly and a federal electoral system of
proportional representation. The United States, with a very high number of fifty states
and extremely decentralized nationwide political parties, is a case in point.
In contrast, in a medium-sized country with a unitary territorial structure but with a
variety of economic interests or cultural allegiances among the intertwined population,
the formation of multiple political parties may push for a sufficiently inclusive assembly
elected by proportional electoral rules, rather than for territorial governments (like, say,
in the Netherlands).
This tradeoff between electoral system and federalism can also involve the size of the
assembly. If the electoral system implies high levels of political party pluralism, the
general assembly must be sufficiently large to capture that pluralism. If, in contrast,
constitution makers privileged the representation of varied territories but were wary of
the perils of multipartism when they chose the electoral institutions (or just imported
them from the colonial metropolis before new rules of proportional representation had
been invented), then the size of the federal assembly can remain relatively small. This is,
in particular, the case of the United States, which has the largest number of territorial
units and both the smallest single-seat electoral district magnitude and the smallest
assembly in proportion to the population. For each country size there can be multiple
equilibrium sets of institutions, but each of the sets involving different combinations of
institutional alternatives will be in equilibrium if it is consistent with certain quantifiable
tradeoffs between institutions.
A potentially fruitful exploration to investigate is the population density of the country
(i.e., the quotient between population and area). Low density usually implies territorial

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dispersion of the population in several distant or separate groups. Even if the country’s
population as a whole is relatively homogeneous in economic and cultural terms, the
costs of governance related to physical distance might make federalism an advisable
formula for a durable democracy. Australia, for one, would be an example of this. If, in
addition to being dispersed, the country’s population taken as a whole is highly
heterogeneous, it is likely that it will be concentrated into separated groups with
relatively high degrees of internal homogeneity, as largely happens, for instance, in
Canada. In any of the cases, nonideological territorial governments could be based on
relatively homogeneous communities, which somehow would replace the representative
and aggregative role of multiple political parties.
On the other side, high population density is likely to imply local heterogeneity, whether
in economic terms, as high density is usually related to high degrees of urbanization and
diversification of economic activity, or in cultural terms, which may be produced by
recent migrations. With this type of structure, federalism may not be a suitable solution
since the creation of small territorial governments would not reduce much the complexity
of the communities, while multiple, nonterritorially based political parties able to
represent different interests and values within a mixed population may require
proportional representation electoral rules (related discussion about Africa appears in
Mozaffar, Scarritt, and Galaich 2003 and Brambor, Clark, and Golder 2007). In fact,
multiple parties successfully pressured for the adoption of proportional representation in
the early twentieth century in a few medium-sized European countries, such as Belgium,
Finland, Norway, and Sweden, soon followed by Austria, Denmark, Ireland, and
Switzerland, and this has spread widely among new democracies in medium-sized
countries across the world in recent decades.
In contrast, in large countries, federalism can be more effective for good governance and
durable democracy than any variant of party systems or electoral rules. Large federal
countries include, for instance, multiparty proportional Argentina, Brazil, Germany, and
South Africa, as well as two-party majoritarian Australia, Canada, and the United States,
while the extremely large size of India has forced both federalism and a multiparty
system in spite of a single-seat electoral system (partly favored by significant territorial
concentration of different ethnic groups in different states and electoral districts).
All in all, political parties tend to be the main actors in the choice of electoral rules, which
they tend to develop in their own self-interest, although under the incentives and limits
imposed by existing rules and procedures for institutional change. Broader sets of other
political institutions, such as basic rules for democracy, voting rights, the representative
assembly, or the territorial structure of the country, can also constrain the processes and
outcomes of electoral system parties’ choice.

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Josep M. Colomer
Josep M. Colomer is Research Professor in Political Science in the Higher Council of
Scientific Research, Barcelona.