British Journal of Political Science

Research Article

Power to the Parties: Cohesion and Competition in the European Parliament, 1979–2001

a1 Department of Government, London School of Economics and Political Science
a2 Université Libre de Bruxelles
a3 Department of Economics, University of California, Berkeley


How cohesive are political parties in the European Parliament? What coalitions form and why? The answers to these questions are central for understanding the impact of the European Parliament on European Union policies. These questions are also central in the study of legislative behaviour in general. We collected the total population of roll-call votes in the European Parliament, from the first elections in 1979 to the end of 2001 (over 11,500 votes). The data show growing party cohesion despite growing internal national and ideological diversity within the European party groups. We also find that the distance between parties on the left-right dimension is the strongest predictor of coalition patterns. We conclude that increased power of the European Parliament has meant increased power for the transnational parties, via increased internal party cohesion and inter-party competition.


a We would like to thank Micael Castanheira, Christophe Crombez, Matthew Gabel, Brian Lawson, Andrew Moravcsik, Keith Poole, Howard Rosenthal, Roger Scully, Michael Shackleton and participants in presentations of the research at the Public Choice Society conference in San Diego, 2002, the European Union Studies Association Conference in Nashville, 2003, Stanford University, the London School of Economics and Political Science, and the University of California, Berkeley, for their comments on earlier versions of the article. We would also like to thank Giacomo Benedetto, Vincenzo Verardi and Elsa Roland for research assistance in the preparation of the article. Research for it was funded by the Economic and Social Research Council of the United Kingdom (Grant No. L213 25 2019), by an ACE grant from the European Commission and by an ARC grant 00/05-252 from the Communauté française de Belgique.