The unexpected empirical consensus among consensus methods

摘要

In economics and political science, the theoretical literature on social choice routinely highlights worst-case scenarios and emphasizes the nonexistence of a universally best voting method. Behavioral social choice is grounded in psychology and tackles consensus methods descriptively and empirically. We analyzed four elections of the American Psychological Association using a state-of-the-art multimodel, multimethod approach. These elections provide rare access to (likely sincere) preferences of large numbers of decision makers over five choice alternatives. We determined the outcomes according to three classical social choice procedures: Condorcet, Borda, and plurality. Although the literature routinely depicts these procedures as irreconcilable, we found strong statistical support for an unexpected degree of empirical consensus among them in these elections. Our empirical findings stand in contrast to two centuries of pessimistic thought experiments and computer simulations in social choice theory and demonstrate the need for more systematic descriptive and empirical research on social choice than exists to date.