From the Bottom up: Measuring Party System Change and Institutional and Electoral Volatility in Both Eastern and Western Europe

Joint paper with Tim Haughton (University of Birmingham) and Fernando Casal Bértoa (University of Nottingham): Since Mainwaring and Scully´s (1995) seminal work, party system stability has been considered to be a necessary condition for the consolidation of democracy. Pedersen´s (1973) index of electoral volatility has been the traditional indicator used to measure such stability. Unfortunately, Pedersen´s index has proved to be an insufficient indicator in those party systems where political parties continuously come and go (Powell and Tucker, 2013). Building on Casal Bértoa et al. (2012), and following the current line of research (Andrews and Bairett, 2014; Weghorst and Bernhard, 2014), this paper introduces a new method for measuring both institutional (i.e. parties) and electoral (i.e. voters) change which is both more reliable and valid. Using a new dataset covering both Western (e.g. Greece, Italy or Spain) and Eastern (e.g. Poland, Macedonia or Moldova) European countries, the paper shows the higher reliability and validity of the new indicator.