A new paper entitled "Central European MEPs as Agents of two Pincipals. Party cohesion in the European Parliament after Enlargement" has been published by András Bíró-Nagy in the 2016/4 issue of the European Quarterly of Political Attitudes and Mentalities. 

This paper investigates the impact of Central European MEPs on party cohesion in the European Parliament. By applying the principal-agent theory, it is also analyzed how loyal are the MEPs of the Czech Republic, Hungary,Poland, Slovakia and Slovenia to their European political groups and national parties. The empirical researchcarried out in this study demonstrates that the Central European MEPs have not brought more division to theirpolitical groups, but have been loyal members of their European parties. The Central European MEPs have notweakened the cohesion of the EP party groups, but party cohesion was even further strengthened between 2004and 2014. Cohesion is the strongest in the biggest parliamentary groups. EPP and S&D set the direction for most politicians on most occasions. Clear ’rebel’ cases, when national parties as a whole went against their European political groups are not more than 2-3 percent of all votes in the two biggest European political families. Nationalparties have a bigger room of manoeuvre in the smaller political groups. In ECR and GUE-NGL the differencebetween loyalty to the national party and the European party group is significantly higher than in EPP and S&D. 

András Bíró-Nagy: "Central European MEPs as Agents of two Pincipals. Party cohesion in the European Parliament after Enlargement" can be downloaded from here.