Capturing time: Measuring the age of party systems

The wide-ranging literature on political development shares a common focus on analyzing changes through time and using continuity as one of its key concepts.1 It is filled with terms like institutionalization, consolidation, or path dependency, which all denote continuity through time. The literature on political development also differentiates levels of continuity using nominal categories like high, medium, or low. These nominal categories are vague and limit the precision with which political development can be analyzed. This paper therefore introduces age as an indicator that allows measuring spatial and temporal variations of continuity in a precise and quantitative fashion. Specifically, it presents the notion of effective party system age (EPSA) to measure the organizational and electoral continuity of party systems. The paper has three parts. First, it describes the basic intuition behind the measure and discusses its operationalization. Second, it illustrates the measure’s utility by presenting a few of the prototypical developmental trajectories that we found in the analysis of 27 post-war party systems. Third, it contrasts EPSA with other widely used party system indicators and demonstrates the distinct ways in which it captures temporal dynamics as well as explicates the distinct ontological assumptions on which it rests