How electoral systems affect MPs ’ positions ∗

The question how different electoral systems affect the represention of voters in parliaments has been a thorny issue for a considerable time. While some research suggests that first-past-the-posts systems should lead to a closer correspondence between the preferences of the electoral district’s median voter and of its representative, other work concludes that in proportional representation systems, especially with open lists, candidates have an incentive to cultivate a strong personal vote. To study this question we take advantage of two peculiarities of the Swiss political system, namely that in the same chamber of the parliament some members are elected in PRand some in plurality elections and that direct democratic instruments play an important role. The second element, given that for a series of votes in parliament voters have to decide on the same issue, allows us to estimate the policy positions of MPs and the median voter of each electoral district in the same policy space. We find that MPs elected in plurality elections are on average closer to their respective median voter. In PR districts, MPs are much more widely spread around the median voters’ preferences. ∗This study has been realized using the data collected in the “Living in Switzerland” project, conducted by the Swiss Household Panel (SHP), which is based at the Swiss Foundation for Research in Social Sciences FORS, University of Lausanne. The project is financed by the Swiss National Science Foundation. It also employs data from the Swiss election studies (http: //www.selects.ch). The paper draws in part on the master’s thesis of Martin (2008) and an earlier version has been presented at the Annual Meeting of the American Political Science Association, Toronto (September 3-6, 2009). Extremely helpful comments by Karen Long Jusko, as well as the help of the Swiss Parliamentsdienste and especially Ernst Firschknecht and Andreas Sidler, who provided the bulk of the empirical data used here and helped us using it, are gratefully appreciated. The Swiss National Science Foundation (Grant No 100012111909) provided generous funding. † Département de science politique, Faculté des sciences économiques et sociales; Université de Genève; 40 Bd du Pont d’Arve; 1211 Genève 4; Switzerland; phone ++41 22 379 83 78; email: [email protected]