On the Robustness of Majority Rule and Unanimity Rule

We show that simple majority rule satisfies four standard< and attractive properties—the Pareto property, anonymity, neutrality, and (generic) transitivity—on a bigger class of preference domains than (essentially) any other voting rule. Hence, in this sense, it is the most robust voting rule. If we replace neutrality in the above list of properties with the weaker property, independence of irrelevant alternatives, then the corresponding robustness conclusion holds for unanimity rule (rule by consensus).