The authors are grateful to Steven Brams, Dennis Mueller, Franz Dietrich, three anonymous referees, and the editors for helpful comments and suggestions. List also acknowledges financial support from the University Center for Human Values, Princeton University, where he was a Visiting Research Scholar during the final stages of this work.
A Conditional Defense of Plurality Rule: Generalizing May's Theorem in a Restricted Informational Environment
Version of Record online: 19 SEP 2006
American Journal of Political Science
Volume 50, Issue 4, pages 940–949, October 2006
How to Cite
Goodin, R. E. and List, C. (2006), A Conditional Defense of Plurality Rule: Generalizing May's Theorem in a Restricted Informational Environment. American Journal of Political Science, 50: 940–949. doi: 10.1111/j.1540-5907.2006.00225.x
- Issue online: 19 SEP 2006
- Version of Record online: 19 SEP 2006
May's theorem famously shows that, in social decisions between two options, simple majority rule uniquely satisfies four appealing conditions. Although this result is often cited in support of majority rule, it has never been extended beyond decisions based on pairwise comparisons of options. We generalize May's theorem to many-option decisions where voters each cast one vote. Surprisingly, plurality rule uniquely satisfies May's conditions. This suggests a conditional defense of plurality rule: If a society's balloting procedure collects only a single vote from each voter, then plurality rule is the uniquely compelling electoral procedure. To illustrate the conditional nature of this claim, we also identify a richer informational environment in which approval voting, not plurality rule, is supported by a May-style argument.