Efficiency in Random Resource Allocation and Social Choice

TL;DR

This paper investigates efficiency in collective choice problems with ordinal preferences and randomization, providing new characterizations and insights into mechanisms like random serial dictatorship across various domains.

Contribution

It offers a unifying framework and new characterizations for when ex-ante and ex-post efficiency coincide in randomized social choice settings.

Findings

Identifies conditions where ex-ante and ex-post efficiency align.

Provides new characterizations for preference profiles.

Analyzes implications for mechanisms like random serial dictatorship.

Abstract

We study efficiency in general collective choice problems where agents have ordinal preferences and randomization is allowed. We explore the structure of preference profiles where ex-ante and ex-post efficiency coincide, offer a unifying perspective on the known results, and give several new characterizations. The results have implications for well-studied mechanisms including random serial dictatorship and a number of specific environments, including the dichotomous, single-peaked, and social choice domains.