Duverger meets Downs in Germany. Duverger’s Law’s Impact on Spatial Voting in a Mixed Electoral System

Since the 1950s, Duverger’s Law is well known in comparative politics. Basically, it states that single-member plurality (SMP) electoral systems tend to favour two-party systems, whereas proportional representation (PR) makes multi-party systems more likely. At the heart of this statement lies the assumption that rational voters try to avoid wasting their votes. Therefore, they do not vote for smaller parties in SMP, even if they prefer these parties to one of the larger parties. However, studies analysing Duverger’s Law on the micro level are scarce. Up to now, there has been no attempt to combine classical theories of electoral behaviour with the Duvergerian macro approach. This paper compares individual vote functions based on a (Downsian) spatial approach for personal and list vote in the recent German parliamentary election (2009). Due to its mixed electoral system combining SMP and PR, Germany constitutes an ideal laboratory for this analysis. A theoretical micro model of the electoral systems’ impact on individual voting decision making is developed proposing that proximity considerations should play a much smaller role voting for a large party in SMP compared to voting for a smaller party. No such differences should exist in PR. First empirical findings indicate that this hypothesis holds true.