Measuring Party System Polarisation with Voting Advice Application Data

Party system polarization is a particularly important concept in comparative politics having been connected to cabinet survival, voter turnout, political stability, ideological voting, and the effectiveness of policy-making. Unfortunately, the available measures of party system polarization are based on imperfect measures of party locations which are subject to projection bias and generally lack reliability and validity. We propose a new measure of party system polarization which is particularly suited for use with the party positions data available in Voting Advice Applications. We illustrate the usefulness of the new measure by comparing the degree of polarization across issues, over time within party systems, and across different party systems.