Explaining Patterns of Party Birth and Death in Western European Parliaments

This study applies the density-dependence model (Hannan & Freeman, 1989) to explain party birth and party death (see also Lowery et al., 2010; 2011). The basic assumption of this model is that organizations in a population rely on the same key resources to exist. As such, they tend to respond similarly to environmental forces, which takes one of two forms: competition or mutualism. A paradox emerges for ideologically similar organizations. The common assumption is that like-minded voluntary and social movement organizations should co-operate, rather than compete, with each other to achieve shared goals; due to resource overlap, however, competition is strongest among these like-minded organizations. In empirical terms, the density-dependence model hypothesizes a U-shaped function for mortality and an inverted U-shape for founding rates. In the beginning an increasing number of organizations fuels the birth of like-minded organization and inhibits mortality among this type of organizations. Yet, at a certain point, density has increased to the extent that competition for similar resources fosters organizational death. As Barnett and Woywode (2004) observe, it is an empirical question whether the observed range of density in the data reaches the point where ideological mutualism is offset by competition based on ideological similarity. Our paper aims to test the generalizability of these dynamics to the area of party competition. Specifically, we test to what extent a U-shaped function for mortality and an inverted U-shape for founding rates explains patterns of party birth and death within different party families (e.g. communists, social-democrat, Christian-democrat, etc.). In addition, we also study whether density in the different party families explains party birth and death in the other party families. These research questions are tested on a dataset containing information for 18 Western European countries on every democratic election that was held from the post-war period onwards (1944-2013).