Income inequality, electoral systems and party polarisation

This study analyses why income inequality and party polarisation proceed together in some countries but not in others. By focusing on the relationship between income inequality, the permissiveness of electoral systems and party polarisation, the study offers a theoretical explanation for how the combination of income inequality and permissive electoral systems generates higher party polarisation. After analysing a cross-national dataset of party polarisation, income inequality and electoral institutions covering 24 advanced democracies between 1960 and 2011, it is found that a simple correlation between income inequality and party polarisation is not strong. However, the empirical results indicate that greater income inequality under permissive electoral systems contributes to growing party polarisation, which suggests that parties only have diverging ideological platforms due to greater income inequality when electoral systems encourage their moves towards the extreme; parties do not diverge when electoral systems discourage their moves towards the extreme.