Working Paper: NBER ID: w25949
Authors: Laurent Bouton; Jorge Gallego; Aniol Llorente-Saguer; Rebecca Morton
Abstract: We study experimentally the properties of the majority runoff system and compare them to the ones of plurality rule, in the setup of a divided majority. Our focus is on Duverger's famous predictions that the plurality rule leads to a higher coordination of votes on a limited number of candidates than the majority runoff rule. Our experiments show that, in contradiction with Duverger's predictions, coordination forces are strong in majority runoff elections. We indeed observe similar levels of coordination under both rules, even when sincere voting is an equilibrium only under majority runoff. Our results suggest that the apparent desire to coordinate, and not vote sincerely, under the majority runoff rule is to some extent not rational. Finally, we find insignificant differences between runoff and plurality systems in terms of both electoral outcomes and welfare. This is so exactly because coordination forces are strong under both rules. But, this does not mean that the two rules are equally socially desirable. Majority runoff rule entails an additional cost: second rounds that take place frequently.
Keywords: majority runoff; plurality rule; voter behavior; Duverger's law
JEL Codes: C92; D72
Edges that are evidenced by causal inference methods are in orange, and the rest are in light blue.
| Cause | Effect |
|---|---|
| majority runoff system (D72) | insincere voting behaviors (D72) |
| plurality rule (D72) | insincere voting behaviors (D72) |
| majority runoff system (D72) | voter coordination (K16) |
| plurality rule (D72) | voter coordination (K16) |
| majority runoff system (D72) | societal costs (J32) |
| majority runoff system (D72) | differences in electoral outcomes (K16) |
| plurality rule (D72) | differences in electoral outcomes (K16) |