A referendum experiment with participation quorums

This paper analyzes a yes/no referendum in which the outcome is valid only if the voter turnout is greater than a predetermined level. Such a participation quorum is argued to induce the minority group of voters to abstain strategically. Such abstention is intended to adversely affect the outcome by achieving a low voter turnout. We first construct a game-theoretic model to derive a theoretical prediction about the relationship between quorums and voting outcomes. It is shown that there exist multiple equilibria, and that strategic abstention can happen if such a participation quorum is imposed. To examine which type of outcome is more likely to be realized, we then conduct a laboratory experiment. We observe that (i) if the quorum is small, all voters go to the polls, and (ii) if the quorum is large, voters in the ex-ante majority group go to the polls, whereas voters in the ex-ante minority group tend to abstain. As a result, it is less likely that the ex-post minority group wins the referendum. However, when the quorum is large, it frequently happens that the outcome is made invalid because of low voter turnout.