We develop and test a theory of voting and turnout decisions that integrates self-interest, social preferences, and expressive motives. Our model implies that if pocketbook benets are relevant, voters either perceive their impact on the outcome to be non-negligible, or expressive motivations do not play a role in the decision on how to vote. Conversely, if own pocketbook benets do not explain voting, then voting is expressive. If the perceived probability of being pivotal is non-negligible, social preferences and expressive concerns are observationally equivalent. Our empirical analysis studies collective choices which are analogous to decisions on local public goods. We consider referenda among university students on whether to collectively purchase deeply discounted at rate tickets for public transportation and cultural amenities. Individual usage data allow quantifying the monetary benets associated with each ticket.As voters had precise information on the individual costs and benets, our setting comprises a real-world laboratory of direct democracy. We nd that monetary benets strongly inuence participation and voting. However, social or expressive motives, such as stated altruism, environmental concerns, and paternalism, are decisive for a signicant minority. Our results rule out purely expressive voting and imply that a substantial share of the electorate perceived their impact on the outcome to be non-negligible.