Ethnic heterogeneity and party system size: A district-level analysis

Abstract

It has been theoretically and empirically shown that ideological diversity complements the effect of institutions on the development of party systems and the number of political parties that ensue. Thus, students of party and electoral systems now commonly employ ethnic fractionalization as an indicator of ideological differences; however, there is no unilaterally agreed upon data set that scholars use. In addition, extant data sets measure heterogeneity at the national level, rather than at the district level, where electoral competition takes place and where both institutional and social factors matter most. Using a multi-level empirical analysis, this article illustrates the interactive effect of the two main district characteristics – magnitude and heterogeneity – on the number of parties. It demonstrates the analytical benefit of using district-level characteristics in explaining party system size and aims to reduce the data gap by providing a district-level ethnic heterogeneity data set for 18 European states.