Turnout and the (effective) number of parties at the national and district levels : A puzzle-solving approach

Abstract

Blais (2006) and Blais and Aarts (2006) in their review essays on voter turnout call attention to a striking puzzle about the link between electoral systems and turnout, namely that, ceteris paribus, proportional representation (PR) systems with many parties appear to have higher national-level turnout than single-member district (SMD) plurality systems with few parties, yet turnout does not increase with the (effective) number of parties (ENP) at the national level. To address this puzzle we turn to district-specific within-nation panel data from Switzerland and Spain. Our country-specific findings allow us to explain the national-level puzzle as essentially an ecological artefact, in that the multi-member districts found in proportional systems, on average, do exhibit higher turnout than SMDs, but turnout does not rise with district magnitude, m, once we move beyond the contrast between m = 1 and m > 1. Using a more sophisticated approach to measuring political competition that does not treat all PR systems as generating identical turnout incentives (Grofman and Selb, 2009), we seek to explain this puzzle by showing both empirically and theoretically that (1) proportionality does not necessarily increase with district magnitude, and (2) competition does not necessarily increase with district magnitude.