Brazil mandates voting for citizens aged 18 to 70 and offers incentives for those outside this range. This study investigates the impact of compulsory voting by examining voter confusion over how the age cutoff applies, using register-based data from six Brazilian elections between 2008 and 2018.

Understanding Voter Confusion: Some voters falsely believe that their obligation to vote depends on one's age during an election year rather than just on Election Day. This misunderstanding is widespread among young voters.

Methodology

* Regression Discontinuity Design (R&D): We analyze voter turnout using R&D, comparing those just below and above the official cutoff date.

* Data Source: Our analysis uses register-based data from actual Brazilian electoral events between 2008 and 2018.

Key Findings

* The legal cutoff is strictly Election Day age. However, many voters incorrectly base their obligation on the election year's age.

* Standard R&D methods focusing solely on the official cutoff date underestimate compulsory voting's impact significantly.

Implications for Research and Policy

* This study demonstrates that voter knowledge of institutional rules can dramatically affect observed outcomes in political research. We caution scholars against assuming their units have full understanding of relevant criteria.