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 proportional representation, politicians’ selection depends on the share of swing voters in the entire electorate. In majoritarian elections, it depends also on the distribution of competitive 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.