The propositions derived in Chapter 2 have identified three factors explaining delegation to and discretion of the Commission and national administrations: decision rules, preferences of the members of the Council, preferences of the Commission and policy complexity. This chapter explains the operationalization of these key independent variables.

The analysis of the dimensions of conflict in EU politics and the related issue of measurement of preferences have been at the center of considerable scholarly attention. This is not surprising. Politics is as much about rules as it is about conflict. Three dominant cleavages have been identified. Political actors in the EU differentiate themselves along their attitudes towards European integration, along lines reflecting different views about substantive policy issues and along the left–right divide. I take these dimensions at face value without prejudging their relative saliency. But I suggest an advancement to the quantitative measurement of these preferences along these cleavages. I also develop a measure of conflict within the Council and use two different methods to operationalize the preferences of the Commission. Finally, I provide a longitudinal analysis of how the Commission's and the Council's preferences have evolved since 1958. An interesting finding from this exercise is with regard to the institutional sources of the pro-integration positions of the Commission. The median voter in the college of commissioners is significantly more supportive of European integration than the pivotal member in the Council under qualified majority voting, even when we consider commissioners as perfect agents of their national government or party.