Sequential unanimity voting rules for binary social choice

Abstract

We consider a group of voters that needs to decide between two candidates. We propose a novel family of neutral and strategy-proof rules, which we call sequential unanimity rules. By demonstrating their formal equivalence to the M-winning coalition rules of Moulin (1983), we show that sequential unanimity rules are characterized by neutrality and strategy-proofness. We establish our results by developing algorithms that transform a given M-winning coalition rule into an equivalent sequential unanimity rule and vice versa. The analysis can be extended to accommodate the full preference domain in which voters may be indifferent between candidates.