A simultaneous analysis of turnout and voting under proportional representation: Theory and experiments

In a system of proportional representation, we study the interaction between a voter’s turnout decision and her party choice, and how these relate to party polarization. Models of strategic interaction with instrumental voting, such as Nash and Quantal Response, predict such interaction effects, while Naive Voting models do not. In particular, the instrumental voting models predict (i) a Polarization Effect: reduced strategic party choice when voting is voluntary makes voters more likely to vote for extreme parties (conditional on voting at all); (ii) an Extremist Effect: voters supporting extreme parties are most likely to vote; (iii) a Turnout Effect: party polarization increases voter turnout. We provide data from a laboratory experiment that provide some support for these theoretical predictions. In addition, we provide supporting empirical evidence from real-world elections. Thus, the interaction between turnout and strategic voting that has been neglected in most of the previous literature is shown to be important, as predicted by models of instrumental voting.