Robust Voting under Uncertainty

This paper proposes normative consequentialist criteria for voting rules under Knightian uncertainty about individual preferences to characterize a weighted majority rule (WMR). The criteria stress the significance of responsiveness, i.e., the probability that the social outcome coincides with the realized individual preferences. A voting rule is said to be robust if, for any probability distribution of preferences, responsiveness of at least one individual is greater than one-half. Our main result establishes that a voting rule is robust if and only if it is a WMR without ties. This characterization of a WMR avoiding the worst possible outcomes complements the well-known characterization of a WMR achieving the optimal outcomes, i.e., efficiency regarding responsiveness.22 p