Reflections on Arrow's theorem and voting rules

摘要

These reflections, written in honor of Kenneth Arrow, sketch out how one political scientist thinks about Arrow's theorem and its implications for voting rules. The basic claim is that Arrow's theorem means that all real-world voting rules are problematic in two quite specific ways-namely, they can be neither 'strategyproof' nor 'spoilerproof'. However, Condorcet's pairwise version of majority rule, while not a fully specified voting rule because of the cyclical majorities problem, is itself both strategyproof and spoilerproof. Moreover, the cycling problem seems to occur only rarely in practice.