Explaining the size of assemblies. A longitudinal analysis of the design and reform of assembly sizes in democracies around the world

Why would parliamentarians vote for a bill reducing the number of seats of their own legislature? After all, this would resemble 'turkeys voting for Christmas.' This question is all the more pressing as the 2008 economic crisis triggered debates about reducing the number of parliamentarians. However, our knowledge of (changes to) assembly sizes is limited. In this study we develop a novel theoretical framework and test it empirically. We advance three main explanations: the gap between the expected size (based on population size) and the actual one, the effective number of parties and perceived voter hostility stemming from economic recessions. We test the framework using OLS regression (1800-2008) and event history analysis (1945-2008) for all democracies. We find a strong connection between population and assembly size when these assemblies are originally designed. Increases in assembly size are influenced by population growth and the effective number of parties. Reductions are influenced mainly by having recently experienced an economic recession.