The study of political parties and party systems is intimately linked to the development of modern political science. The configuration of party competition varies across time and across polities. In order to capture this variance, one needs to go beyond the analysis of individual parties and to focus on their numbers (i.e. fragmentation), their interactions (i.e. closure), the prevailing ideological patterns (i.e. polarization), and the stability of the balance of power (i.e. volatility) in all spheres of competition, including the electoral, parliamentary, and governmental arenas. Together, these factors constitute the core informal institution of modern politics: a party system. The relevant scholarship relates the stability of party systems to the degree of the institutionalization of individual parties, to various institutional factors such as electoral systems, to sociologically anchored structures such as cleavages, to economic characteristics of the polity (primarily growth), to historical legacies (for example, the type of dictatorship that preceded competitive politics) and to the length of democratic experience and to the characteristics of the time when democracy was established. The predictability of party relations has been found to influence both the stability of governments and the quality of democracy. However, still a lot is to be learned about party systems in Africa or Asia, the pre-WWII era or in regional and/or local contexts. Similarly, more research is needed regarding the role of colonialism or how party system stability affects policy-making. As far as temporal change is concerned, we are witnessing a trend towards the destabilization of party systems, but the different indicators show different dynamics. It is therefore crucial to acknowledge that party systems are complex, multifaceted phenomena.
