Less Is Not More: The Insufficiency of Current Data for Understanding the Relationship between Social Diversity and Party System Development

Abstract

Scholars commonly argue that in democratic societies, the size or fragmentation of party systems — as well as other important features of party systems, such as their nationalization or aggregation — is a function of social heterogeneity, in interaction with political institutions such as the electoral system. Although societies exhibit different types of heterogeneity, from their religious diversity to how socioeconomically equal they are, and although heterogeneity often varies at different political levels, from the national level to the electoral district, political scientists typically characterize countries’ heterogeneity almost exclusively according to measures of national level ethnic diversity. We draw attention to the importance of both different types of heterogeneity and the level at which social heterogeneity is measured. Using original census data for a number of advanced industrial and developing democracies, we show that characterizing heterogeneity solely according to nationwide ethnic diversity often paints a misleading portrait, particularly where it matters the most: at the level of the electoral district. We conclude briefly with the implications for theories that seek to relate social heterogeneity to key aspects of democratic party systems.