Expert surveys offer greater opportunities for researchers to study topics for which there is scarce information. The key advantage of our survey approach is that it overcomes the time-invariant element of existing Europeanisation measures for the periods between treaties. With our method we sought to produce a more comprehensive picture of the progression of European integration in individual policy areas.

245 experts completed the survey in nine policy areas (corresponding to the nine configurations of the Council of the EU). Moreover, 28 subfields were also included in the survey. On average, there are 27 expert responses per policy area for the Europeanisation index. The fieldwork was completed over 10 months. We selected the experts based on published scientific research in each policy area.

The survey had four main sections: a general section including control questions, and three sections corresponding to the three areas of interest:

• temporal assessment of the pace of Europeanisation in each policy area,
• temporal assessment of the ideological leaning of EU legislation,
• a cross-national comparison of Europeanisation across member states.