Hitotsubashi Institute for Advanced Study


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.

Report No.: HIAS-E-60
Author(s): Satoshi Nakada(a)
Shmuel Nitzan(b), (c)
Takashi Ui(a)
Affiliation: (a) Graduate School of Economics, Hitotsubashi University
(b) Department of Economics, Bar-Ilan University
(c) Hitotsubashi Institute for Advanced Study, Hitotsubashi University
Issued Date: December 2017
Keywords: majority rule, weighted majority rule, responsiveness, Knightian uncertainty
JEL: D71, D81