Subnational Patterns of Participation: Compulsory Voting and the Conditional Impact of Institutional Design

Cross-national studies of turnout find that compulsory voting has the strongest impact on participation, boosting turnout by 10 to 18 percent. We argue that in the absence of compulsory voting, other institutional factors such as small district size, strong electoral competition, and moderate candidate fragmentation may be similarly effective at mobilizing turnout. Where voting is mandatory, these factors should instead primarily influence how people vote once they are at the polls—diminishing levels of invalid voting, and consequently increasing effective turnout. We take advantage of the abolition of compulsory voting in Chile to test our expectations immediately before and after reform, in the exact same electoral districts. Using this unique subnational research design, we leverage data from more than 1,000 mayoral elections over the course of three electoral cycles and across 345 municipalities to examine patterns of turnout and invalid voting. Results show that small district size, strong electoral competition, and moderate candidate fragmentation are effective at reducing invalid voting when turnout is compulsory, and fostering higher levels of turnout when voting is voluntary.