Party Group Switching in the European Parliament: A Quantitative Analysis, 1979-2009

Friday, July 14, 2017
Court/Senate (University of Glasgow)
Aaron Russell Martin , Political Science, Loyola University Chicago
Members of the European Parliament (MEPs) switch party groups more frequently than the members of national parliaments (Evans and Vink 2012; O’Brien and Shomer 2013). This paper rests on the theoretical assumption that the European Parliament’s (EP) party system is “unevenly” institutionalized and divided into two blocs—a fully institutionalized cartel of party groups and a periphery bloc that is weakly institutionalized (Randall and Svåsand 2002). This asymmetry should lead to more switching among periphery members. As the first paper to statistically analyze group switching across multiple EP sessions, this examination makes several contributions to the literature. First, it measures policy distance on two dimensions, making it possible to determine whether MEP incongruence with the party group on the ideology axis, or on the integration axis, is the most significant proximate cause for switching. Next, by introducing a categorical dependent variable which operationalizes “types of switch,” this study examines the direction and frequency of reaffiliation based on remote causes associated with the EP’s party system.

The unique data set—assembled using Høyland et al.’s EP data (2009), Ray’s political party data (1999), the Chapel Hill Expert Survey data (2015), and DW Nominate scores calculated by Keith Poole—includes every MEP between 1979 and 2009, their ideal point in a two-dimensional space, and each national delegations’ position in that same space. Using multinomial logistic regression models, preliminary tests indicate that, while MEPs initially choose a group based on ideological affinity (McElroy and Benoit 2010), incongruence on the integration dimension is associated with group exit.

  • Party_Group_Swiching_in_the_EP_CES_2017_Aaron_Martin.pdf (881.6 kB)