Most research into electoral systems focuses on their effects. Only recently has a significant literature emerged examining how they are chosen. This chapter explores four core issues in that literature. First, it considers what is meant by “electoral system change.” This can refer to changes of any scale to any electoral rules in any context, but typically—including here—a narrower definition is used. Second, the chapter investigates what electoral system changes happen. It considers the frequency of reforms and patterns in those reforms. Third, it examines the determinants of electoral system change. Most studies focus on the microfoundations of reform. Others highlight the systemic level. Both perspectives are needed to develop a complete picture. Finally, the chapter gauges the effects of electoral system change and assesses why such changes, notwithstanding important effects, often fail to deliver on their promoters’ expectations.
Robert G. Moser, Ethan Scheiner, and Heather Stoll
Scholars commonly argue that in democratic societies, the size (or fragmentation) of party systems is a linear function of social heterogeneity, in interaction with political institutions such as the electoral system. This “interactive hypothesis” has generated a large body of research, mostly in support of its fundamental claims. Despite the prominence of this literature, there is also a growing body of research that casts doubt on the interactive hypothesis. Although societies exhibit a variety of different types of heterogeneity, from religious to socioeconomic diversity, which vary within countries by subnational region, political scientists typically characterize countries’ heterogeneity almost exclusively according to measures of national-level ethnic diversity. This chapter uses original census data to show just how misleading such a characterization can be. We conclude with the implications for theories that seek to relate heterogeneity to key aspects of democratic party systems.