Why Waste Your Vote? Informal Voting in Compulsory Elections in Australia

In Australia, where voting is compulsory, around 5% of votes are informal, not counting toward the outcome. Between 2004i?½2016, 32% of electorates reported more informal votes than votes in the margin between the winner and runner-up. Using exogenous changes in electorate boundaries, we test two hypotheses from the literature. We find the pivotal voter theory unsupported, except that better-educated voters respond to the margin more strategically. However, we do find that more candidates cause more informal votes. This choice-overload effect is observed regardless of votersi?½ education, indicating the role of time and effort cost rather than just cognitive ability.