Two-stage majoritarian choice

About this event

We propose a class of decisive collective choice rules that rely on a linear ordering to partition the majority relation into two acyclic relations. The first relation is used to obtain a shortlist of the feasible alternatives while the second is used to make a final choice. Rules in this class are characterized by four properties: two classical rationality requirements (Sen’s expansion consistency and Manzini and Mariotti’s weak WARP); and adaptations of two classical collective choice requirements (Arrow’s independence of irrelevant alternatives and Saari and Barney’s no preference reversal bias). These rules also satisfy some other desirable properties including a version of May’s positive responsiveness.