Party System Institutionalization

Conceptualized as “the process by which the patterns of interaction among political parties become routine, predictable and stable over time”, party system institutionalization (PSI) is measured according to the following composite index:

iPSI = (sIGA+IFA+IC)/3

where IGA is the index of government alternation, IFA is the index of familiar alternation and IC is the index of closure (see: Casal Bértoa 2012: 453-454; 2016; Casal Bértoa and Mair, 2012; and, especially, Casal Bértoa and Enyedi, 2016). For more details, see codebook and video.

Please cite the following database as: Casal Bértoa, F. (2016): Database on WHO GOVERNS in Europe and beyond, PSGo. Available at: