Party system nationalization

Abstract

The existing measures of party system nationalization and territorial heterogeneity of electoral support, including the Gini-based system-level nationalization score and its complements, can be inappropriate in those research contexts where, as it is in the study of federations, the territorial structure of the state is a substantively important factor of political development rather than one of the possible levels of electoral data aggregation. This problem can be solved by using a normalized version of the Gini coefficient. Alternatively, it is possible to use a new measure, the index of party system nationalization proposed in this study. While both the normalized Gini-based index and the new measure fully satisfy all theory-inspired requirements and yield similar results, the new measure may be preferable because of its relative computational simplicity and intuitively easy understanding.