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

In Australia, where voting is compulsory, around 5 per cent of votes are informal, not counting toward the outcome. Between 2004 and 2016, 32 per cent 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 voters' education, indicating the role of time and effort cost rather than cognitive difficulty.