The Number of Parties and Party System Nationalization in an Integrated Analytical Framework
This study develops a methodological tool for integration of research on party system fragmentation and party system nationalization. The method is built by decomposing a standard indicator of fragmentation, the effective number of parties, into individual-party components (effective size scores), and weighting them by nationalization scores, which allows for disaggregating the number of parties into two distinct components, the effective numbers of national and regional parties. As a result, it becomes possible to assess the influences of substantively important factors upon the components of the number of parties and the overall level of fragmentation in a methodologically consistent, quantifiable way. In addition, the proposed framework of analysis differentiates between direct and indirect effects upon party system fragmentation. A preliminary empirical test on a sample from 90 countries demonstrates that the proposed framework for analysis allows for achieving a rich and nuanced understanding of the factors of party system fragmentation.