Compulsory voting (CV) is a system of laws and/or norms mandating that enfranchised citizens turn out to vote, often accompanied by (a) a system of compulsory voter registration, and (b) penalties for non-compliance, usually fines or the denial of state-provided benefits. CV is widespread throughout Latin America, but somewhat rarer among industrialized democracies. Cross-national studies find CV to be an effective mechanism for increasing turnout, by between seven and sixteen percentage points; within-country comparisons also generally find that CV boosts turnout. CV is commonly thought to advantage parties of the left (based on social-structural and demographic patterns of turnout in countries without CV), and hence also shift public policy in that direction. But these conjectures are difficult to verify, since other political and institutional variables intervene between voter turnout, election outcomes and policy outputs. Fines and sanctions are just one aspect of CV: states employing CV usually reciprocate by reducing the costs of turnout for its citizens, via weekend voting, simple registration procedures, and the creation of a centralized, professional bureaucracy concerned with all aspects of election administration.