Runoff Elections in the Laboratory

We study experimentally the properties of the majority runoff system and compare them to those of plurality rule. Our focus is on Duverger’s famous prediction that the plurality rule leads to higher coordination of votes on a limited number of candidates than the majority runoff rule. We find strong coordination forces under both systems. However, as predicted by the theory, in some cases these forces are stronger under plurality. Despite these differences in voting behavior, we find small and mostly not significant differences in electoral outcomes and hence voters’ welfare.