Electoral Institutions, Social Diversity and Fragmentation of Party Systems: A Reassessment

The article examines the determinants of party fragmentation based on electoral district data from the Swiss cantons (2010‐2015). In contrast to previous studies, three different dependent variables are taken into account: firstly, the raw number of parties, secondly, the effective number of parties based on vote shares and, thirdly, the effective number of legislative parties. On all three levels, the exclusion magnitude proves to be the most important factor. Compared to this, other institutional variables contribute little explanatory power. However, apparentments are relevant in the first stage of our analysis as they increase the raw number of parties standing for election. In terms of sociological factors, we only find limited relevance. Denominational and linguistic heterogeneity do not have any impact. This can be explained by the fact that linguistic heterogeneity is only weakly pronounced at district level. The finding emphasises the importance of district‐based data for the analysis of party system fragmentation in general