Magnitude matters: Voter turnout under different electoral systems

Abstract

Do voters participate more under proportional than plurality systems? While existing research typically suggests proportional representation (PR) systems exhibit higher turnout than majoritarian systems, several studies indicate a less clear-cut relationship between proportionality and voter turnout. Using a regression discontinuity design, we analyze constituency-level data from Polish municipal elections (1998-2010) to compare three electoral systems: single-member district plurality (SMDP), multi-member district plurality (MMDP), and open-list proportional representation (OLPR). This institutional setting allows us to examine both electoral formula and district magnitude effects through two transitions: from SMDP to OLPR (changing both formula and magnitude) and from MMDP to OLPR (changing primarily formula). We find that PR increases turnout by 3-4 percentage points compared to SMDP but shows no significant differences compared to MMDP. These contrasting effects suggest that district magnitude, not just electoral formula, shapes voter participation. Our findings challenge the view that proportional representation inherently increases voter participation by showing that turnout differences emerge primarily from the shift to multi-member districts. The results demonstrate how the interaction between district magnitude and electoral formula affects voting behavior, moving beyond the simple majoritarian-proportional dichotomy.