Another strategy-proofness characterization of majority rule

Abstract

Campbell and Kelly (2015) proved that, for m≥4 alternatives and n≥3 individuals, majority rule is the only social choice function defined on the Condorcet domain that satisfies strategy-proofness, anonymity, and neutrality. They left open the question whether these three properties characterize majority rule when n is a multiple of four and m is equal to three. We prove their characterization does hold in this case and in the process we give another characterization of majority rule.