United we stand: Constituency homogeneity and comparative party polarization

We argue that party polarization is a function of parties' distances, their internal homogeneity, and their relative sizes. While existing measures in political science incorporate the first and last feature, party homogeneity is typically neglected. Since virtually all polarization measures in one way or another incorporate distance, we suggest a simple way to adjust distance measures for party homogeneity. We then examine levels and trends of polarization in nine OECD countries using a newly collected data-set which includes left–right party positions based on both expert and mass surveys.