Voters are rational

We test whether voters are rational in the sense that their decision to vote depends on its expected impact on the election outcomes. By using exogenous variation in pivotal probabilities that arise at population thresholds determining council sizes in Finnish municipal elections, we provide the first causal evidence on this rational voting hypothesis. We find statistically significant, economically relevant and robust effects of crossing the threshold on turnout. Furthermore, we use a novel instrumental variables design to show that the changes in the pivotal probabilities rather than simultaneous changes in available candidates drive the results. Thus, the rational voter exists.