Electoral Rules and the Party Composition of Governments: Why Are There Social Democratic and Liberal Welfare States?

Left governments redistribute more than right governments. But why are some countries predominantly governed by social-democratic (left) parties whereas others are dominated by conservative (right) parties? Recently, scholars have pointed to the effects that electoral rules have on the ideological composition of governments. Majoritarian electoral systems seem to increase the electoral chances of conservative parties, whereas PR seems to favour the left. One causal mechanism may lie in the incentives for the median voter to support centre-right candidates in majoritarian systems and centre (left) parties in PR systems. Another may be that the mechanics of the vote-seat translation in majoritarian systems disadvantage parties of the left. In this paper we look at the entire democratic delegation chain from voters to parliaments to governments and ask how electoral rules and their effects may favour some parties over others. We highlight the intermediate effect of party system fragmentation on the right and on the left. Empirically, we draw on a data set that includes advanced democracies over the entire post war period. Our results show, that single member plurality elections are indeed ‘bad for the left’ and increase the number of centre-right governments. Our finding for PR systems is more mixed and we find a dominance of centre-left cabinets especially in the first post-war decades.