Voting for Pareto optimality: a multidimensional analysis

Abstract

We compare unanimity rule and majority rule in their abilities to produce Pareto superior and Pareto optimal alternatives in fixed number of rounds of voting using a two-dimensional spatial voting model with random proposals, sincere proposals, and strategic proposals. Our findings show that for random or sincere proposals, majority rule is at least as likely to select a Pareto optimal outcome as unanimity rule. For strategic proposals, the subgame perfect equilibrium under unanimity rule is Pareto optimal. For other k-majority rules, the outcome is Pareto optimal or very close to it. For outcomes that are both Pareto optimal and Pareto superior, unanimity rule outperforms majority rule.