Political selection under alternative electoral rules

We study the patterns of political selection in majoritarian versus proportional systems. Political parties face a trade off in choosing the mix of high- and low-quality candidates: high-quality candidates are valuable to voters, and thus help to win elections, but they crowd out loyal candidates, who are most preferred by the parties. Under pro- portional representation, politicians’ selection depends on the share of swing voters in the entire electorate. In majoritarian elections, it depends also on the distribution of compet- itive versus safe (single-member) districts. We show that a majoritarian system with only a few competitive districts is less capable of selecting good politicians than a proportional system. As the share of competitive districts increases, the majoritarian system becomes more efficient than the proportional system. However, for a large enough share of competitive districts, a non-monotonic relation arises: the marginal (positive) effect of adding high-quality politicians on the probability of winning the election is reduced, and highly competitive majoritarian systems become less efficient than proportional ones in selecting good politicians.