Electoral Systems in Latin America: Explaining the Adoption of Proportional Representation Systems During the Twentieth Century

Latin American Politics and Society, Fall 2009 by Wills-Otero, Laura

ABSTRACT

This article explains the twentieth-century Latin American shift from majoritarian to proportional representation (PR) electoral systems. It argues that PR was introduced when the electoral arena changed significantly and threatened the power of the dominant party. The adoption of PR was therefore an effort by the established party to retain partial power in the face of absolute defeat. Majoritarian systems remained in place when the incumbent party was strong enough to believe that it could gain a plurality of the votes despite electoral changes. An empirical analysis of 20 countries over 104 years (1900-2004) provides support for this argument.

In 1900, no Latin American country allocated legislative seats with proportional representation (PR), but by the middle of the twentieth century, half the region had adopted such an electoral rule, and today all but three countries still employ this system.1 What explains the movement from a restrictive majoritarianism to a structure that encourages political party competition? This study argues that PR - and more broadly, adjustments to open the electoral system - is introduced when changes in political conditions threaten the hegemony of the dominant party. A shift to PR therefore reflects an effort by the established party to retain partial power when facing the prospect of losing all power under majoritarian rules.

More specifically, this study proposes that three phenomena threaten entrenched party dominance: an influx of voters to the electorate; the advent of new political parties that capture a substantial number of votes from the dominant party; and a shift in the preferences of the electorate away from the major party. As new or oppositional parties become stronger and newly enfranchised voters from previously politically marginalized social classes, the middle and working classes, begin to support these parties, failure to adopt PR would lead to the absolute defeat of the ruling party; and this prospect generates pressure on party leaders to strategically adjust the existing electoral system in the direction of PR.

Similar theories have been advanced for industrialized democracies (Boix 1999; Rokkan 1970).2 This study expands these theories to the Latin American context by proposing that the regional adoption of PR occurred for a reason similar to that of developed countries: a calculation made by ruling parties perceiving a credible threat to their dominance under majoritarian electoral systems. This argument is elaborated by suggesting that restrictive majoritarian systems are maintained when the incumbent party is strong enough to believe that it can gain a plurality of votes despite an increase in the voting population, the emergence of new parties, or a shift in electoral preferences. The theory presented here also explains adjustments to the degree of electoral system proportionality, since openings may emerge not only by adopting PR, but also by increasing the district magnitude (DM) under PR or by reducing it under majoritarianism.3 The literature on electoral system choice has emphasized the shift from one allocation rule to another but has not considered changes in proportionality. The empirical models for this study are based on statistical results from an analysis of a new electoral systems dataset of 20 Latin American countries from 1900 to 2004.4

ELECTORAL SYSTEMS AS A DEPENDENT VARIABLE

The literature on electoral systems is unbalanced, with most attention focused on the consequences of electoral systems for political stability and on the number of political parties in both representative institutions and the electorate (Cox 1997; Duverger 1954; Laakso and Taagepera 1979; Rae 1967; Sartori 1976; Taagepera and Shugart 1989). These studies have concluded that in addition to the electoral formula, the most relevant feature is the district magnitude. Indeed, evidence indicates that "the more legislators per district, the smoother the road for new parties" (Willey 1998).5

Fewer studies have addressed the origins of electoral rules, probably because such electoral modifications are rare and usually occur only in periods of extraordinary political change. Research for advanced democracies has devoted attention to the introduction of PR at the beginning of the twentieth century (Boix 1999; Rokkan 1970), and to the dynamics of electoral reforms and their impact on party systems. In Latin America, a relatively large amount of research has been conducted since the early 1990s, including case studies that analyze the transformation or stability of electoral systems (Mainwaring 1999; Siavelis 1997), as well as data accumulation regarding the different dimensions of electoral rules, including electoral formulas, electoral thresholds, district magnitudes, and ballot structures (Colomer 2004; Coppedge 1997; Golder 2003; Jones 1995a, b; Lundell and Karvonen 2003; Nohlen 1993, 2005b; Wallack et al. 2003).

In addition, some scholars have addressed the determinants of the choice of electoral rules after Latin American countries moved from authoritarian regimes to democratic governments in the 1980s (Ames 1995, 2001; Crisp 2000; Jones 1995a; Nielson 2003; Siavelis 1999; Tsebelis 1995; Wallack et al. 2003), but few have attempted to explain the origins of electoral systems before the third wave of democratization. In fact, a recent work about the choice of rules to elect Latin American presidents is the only systematic comparative analysis that deals with long-term electoral reform processes (Negretto 2006). Two other efforts have devoted attention to historical factors that determined the adoption of electoral systems in the first half of the twentieth century, but both possess information gaps: Colomer (2004) lacks detailed information about the average district magnitude for each country-year, while Nohlen (2005b) lacks data about rule specificities at the beginning of the century and utilizes case studies rather than a systematic comparative analysis. The new dataset used for the present study fills these gaps and contributes to the literature on the origin of electoral rules. This article therefore represents the first attempt to understand the adoption of PR in twentieth-century Latin America.