Voting patterns and alliance formation in the European Parliament.

Members of the European Parliament (MEPs) have voluntarily formed transnational political groups and invariably follow the voting instructions of these groups. This is intriguing as there are few obvious incentives for doing so. Unlike national parties, for example, the political groups in the European Parliament are not punished by the electorate if they are divided on key issues, as citizens know very little about what goes on inside the European Parliament. This paper pieces together an explanation of why the European political groups exist and why they have become so powerful by looking at the determinants of group cohesion and by undertaking a spatial analysis of voting in the European Parliament. MEPs who share preferences on a range of issues on the European Union policy agenda have an incentive to establish a division-of-labour contract and to share the costs of collecting information. Once internal party policy specialization and agenda setting has been established, MEPs have incentives to follow the voting instructions of their group owing to the advantages of cohesion in a context of repeated voting.