Effects of electoral institutions and social diversity on party systems

Official URL: https://risc01.sabanciuniv.edu/record=b2748684_(Table of contents)

How do social heterogeneity and electoral system permissiveness influence party system size? Duverger’s conditional hypothesis is one of the most prominent answers to this question. To test this hypothesis, in the second chapter, I conduct a cross-national analysis focusing on fixing the drawbacks of previous studies. The preliminary analyses in this chapter point out how these drawbacks can influence the findings. The main analyses test Duverger’s hypothesis by using data at the appropriate aggregation level and introducing an a priori agnostic measure of social diversity. Our findings make us more confident that Duverger’s hypothesis finds empirical support. The subsequent chapter, which focuses on the six general elections between 2002 and 2018 in Turkey, delves deeper into the mechanism behind Duverger’s hypothesis. It is shown that despite the 10 percent nationwide threshold, the mechanical effect of electoral district permissiveness is present, depending on the electoral geography and election year. Moreover, the findings demonstrate that the threshold, by forcing parties to maximize their national vote share, prevent Duverger’s assumed district-level strategic rationality to hold. Furthermore, we see that in the absence of such a nation-level constraint, Kurdish nationalist parties in the 2007 and 2011 elections implemented an electoral strategy in line with the district-level rationality assumed by Duverger, but a similar behavior on part of those parties’ supporters is not observed.