Twenty years after they were characterized as under-institutionalized, most of the party systems in Latin America have not only failed to institutionalize, but have actually de-institutionalized, while a select few have collapsed. This paper examines these trends conceptually and empirically. We re-structure the concept of party system institutionalization (PSI) in light of findings in the existing scholarship on the topic, arguing that PSI should be understood as stability in the patterns of competition. We identify three defining features of the concept: the stability of the main actors, the stability in vote shares from one election to the next, and the main parties’ programmatic stability. We use these features to define party system collapse and distinguish it from the processes of de-institutionalization and re-alignment. Finally, we propose two new indicators of PSI and present the main empirical indicators of PSI for eighteen Latin American countries.
