Altruism and voting: A large-turnout result that does not rely on civic duty or cooperative behavior

I propose a game-theoretic model of costly voting that predicts significant turnout rates even when the electorate is arbitrarily large. The model has two key features that jointly drive the result: (i) some agents are altruistic (or ethical), (ii) among the agents who prefer any given candidate, the fraction of altruistic agents is uncertain. When deciding whether to vote or not, an altruistic agent compares her private voting cost with the expected contribution of her vote to the welfare of the society. Under suitable homogeneity assumptions, the asymptotic predictions of my model coincide with those of Feddersen and Sandroni [12] up to potential differences between the respective parameters that measure the importance of the election. I demonstrate with an example that these homogeneity assumptions are not necessary for qualitative predictions of my model. I also show that when the fractions of altruistic agents are known, turnout rates will typically be close to zero in a large election, despite the presence of altruism.