The issue of unequal electoral turnout poses serious concerns for both the overall health of democratic politics, and the extent to which certain groups exert an unequal influence on the political process. This article explores the relationship between electoral rules such as: compulsory voting, electoral system proportionality, and voter registration with voter inequality in terms of age, income and education. This is examined using cross-national survey data and cross-level interactions between electoral institutions and socio-demographic variables. The final dataset is based on waves 2–4 of the Comparative Study of Electoral Systems, and contains information on 133,000 individuals, within 45 countries, between 2001 and 2016. The results indicate that compulsory voting is associated with a significant reduction in turnout inequalities, while the effects of proportionality and voter registration are somewhat more mixed.