Electoral systems' effects on participation beyond turnout

• Department of Political and Social Sciences

This session of the Political Behaviour Colloquium features a presentation by Leonardo Carella, Postdoctoral Researcher and Lecturer at University of Vienna.

How does proportional representation (PR) affect voters' willingness and ability to express their preferences at the ballot box, and with what consequences for biases in participation? This paper starts by showing that the effect of electoral rules on invalid voting can be as large as their effect on turnout rates (or larger). I then argue that PR affects rates of invalid voting via two distinct channels. By increasing voters' choice and efficacy relative to majoritarian systems, PR decreases occurrences of intentional invalid voting; by increasing ballot complexity, PR increases occurrences of unintentional invalid voting. Both effects come with an educational bias: gains in effective participation from reductions in rates of intentional invalid voting are larger when the electorate is politically sophisticated, while participation losses from higher rates of unintentional invalid voting under more complex ballot structures are larger among electorates with lower levels of political sophistication. I present evidence for both mechanisms, as well as the resulting implications for effect heterogeneity, from regression discontinuity analysis of rates of blank and null in local election data from Italy (1964--1970) and Poland (2018--2024), where municipalities are assigned to proportional or majoritarian systems according to a sharp population cut-off. I conclude by discussing implications for electoral system design with a view to countering inequalities in participation.

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