Mechanical and political consequences of electoral systems. A dynamic perspective

Research on electoral systems has generated deep insights into their mechanical and psychological effects on party system size. Nonetheless, four methodological problems constrain the robustness of previous findings. First, the classical cross-sectional design of most studies does not allow to control for all relevant variables; second, several models suffer from omitted variable bias; third, existing studies often neglect time trends; and fourth, the so called endogeneity problem remains unsolved. The quasi-experimental longitudinal design of our paper allows us to contribute to a solution to these methodological complexities and thus to analyze the dynamics of the relationship between electoral institutions and party system size. For this purpose, we focus on the consequences of electoral system changes at the constituency level. Thereby, this paper aims to answer two questions: (a) whether change in electoral systems has observable short- and long-term consequences on the size of electoral and legislative party systems and (b) whether these effects can be explained by established theories on the effects of electoral systems. Our time-series cross-sectional analysis draws on all OECD and/or EU-member states since the introduction of the universal male suffrage.