On Plurality Voting and Runoff Elections: Information Aggregation under Divided Majority

This article compares Plurality Voting (PV) and two forms of Runoff Elections (RE) in a setting in which (i) there are two majority-preferred alternatives, (ii) a strong minority backs a third alternative which would make the majority strictly worse off, and (iii) some of the majority voters are uninformed about the "correct" majority alternative. I show that in the informative equilibrium in Majority Runoff Elections (MRE), uninformed majority voters vote randomly with strictly positive probability, achieving partial information aggregation, while they always abstain in Automatic Runoff Elections (ARE), achieving full information aggregation and strictly improving the majority's welfare. However, uninformed majority voters do not abstain in PV, resulting in less information aggregation than in both MRE and ARE.

On Plurality Voting and Runoff Elections: Information Aggregation under Divided Majority

This article compares Plurality Voting (PV) and two forms of Runoff Elections (RE) in a setting in which (i) there are two majority-preferred alternatives, (ii) a strong minority backs a third alternative which would make the majority strictly worse off, and (iii) some of the majority voters are uninformed about the "correct" majority alternative. I show that in the informative equilibrium in Majority Runoff Elections (MRE), uninformed majority voters vote randomly with strictly positive probability, achieving partial information aggregation, while they always abstain in Automatic Runoff Elections (ARE), achieving full information aggregation and strictly improving the majority's welfare. However, uninformed majority voters do not abstain in PV, resulting in less information aggregation than in both MRE and ARE.

On Plurality Voting and Runoff Elections: Information Aggregation under Divided Majority

This article compares Plurality Voting (PV) and two forms of Runoff Elections (RE) in a setting in which (i) there are two majority-preferred alternatives, (ii) a strong minority backs a third alternative which would make the majority strictly worse off, and (iii) some of the majority voters are uninformed about the "correct" majority alternative. I show that in the informative equilibrium in Majority Runoff Elections (MRE), uninformed majority voters vote randomly with strictly positive probability, achieving partial information aggregation, while they always abstain in Automatic Runoff Elections (ARE), achieving full information aggregation and strictly improving the majority's welfare. However, uninformed majority voters do not abstain in PV, resulting in less information aggregation than in both MRE and ARE.

Measuring the Competitiveness of Elections

The concept of electoral competition plays a central role in many subfields of political science, but no consensus exists on how to measure it. One key challenge is how to conceptualize and measure electoral competitiveness at the district level across alternative electoral systems. Recent efforts to meet this challenge have introduced general measures of competitiveness which rest on explicit calculations about how votes translate into seats, but also implicit assumptions about how effort maps into votes (and how costly effort is). We investigate how assumptions about the effort-to-votes mapping affect the units in which competitiveness is best measured, arguing in favor of vote-share-denominated measures and against vote-share-per-seat measures. Whether elections under multimember proportional representation systems are judged more or less competitive than single-member plurality or runoff elections depends directly on the units in which competitiveness is assessed (and hence on assumptions about how effort maps into votes).