Alternatives to plurality rule for single-winner elections: When do they make a difference?

Declining levels of turnout and growing distrust in political elites are often seen as symptoms of a crisis of representative democracy. Various proposals of reform have been made to reinvigorate representation and political participation. This paper focuses on one aspect of that debate: finding an alternative to FPTP, which is the electoral rule most frequently used in single-member districts, but which is criticized, among others, for allowing only a limited expression of voters' preferences. Many alternative rules are in use or have been suggested, such as Two-Round majority, Instant Runoff, Approval Voting, Majority Judgement, or Range Voting. The literature on these decision rules has concentrated on their formal properties. Yet, we know surprisingly little about how frequently these rules would lead to different outcomes in normal electoral settings. This paper improves our understanding of these rules by examining their mechanical effects. We start from data on voters' party utilities from "real-world" settings, based on CSES data. This allows simulating and comparing the outcomes of different electoral rules under a variety of distributions of voters' party preferences. We then analyze how frequently they lead to different outcomes and identify the contextual characteristics that explain these differences. For the latter question, we focus on a number of party system or electorate's characteristics, which have been highlighted in debates on challenges to representation (such as ideological polarization, party system fragmentation, or affective polarization).