National interests in the European parliament: Roll call vote analysis

Abstract

We propose a method for identifying national interests in the European Parliament by comparing roll call vote results with MEPs’ expected ideological positions. We define a new measure – national shift index, corresponding to the magnitude of national delegation’s shift from the aggregate ideological position – which quantifies the influence of the national interest on the voting results. Using this measure, we identify issues characterized by strongest dominance of national factors and compare national delegations’ propensity to vote along national lines.