Social Diversity, Electoral Systems, and the Party System
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.