How electoral systems affect MPs’ positions

Abstract

The question how different electoral systems affect the representation 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 (PR) 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 PR and 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 members of parliament (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.