Turnout Across Democracies

World democracies widely differ in electoral rules, as well as in legislative, executive or legal institutions. Different institutional environments induce different mappings from electoral outcomes to the distribution of power. We explore how these mappings affect voters' participation to an election. We show that the effect of such institutional differences on turnout depends on the distribution of voters' preferences for the competing parties. In particular, we uncover a novel contest effect: given the distribution of preferences, turnout increases and then decreases when we move from a more proportional to a less proportional system; turnout is maximized for an intermediate degree of proportionality. Moreover, we generalize the competition effect, common to models of endogenous turnout: given the institutional environment, turnout increases in the ex-ante closeness of the election and peaks when the population is evenly split between the two parties. These results are robust to a wide range of modeling approaches, including ethical voter models, voter mobilization models, and rational voter models.