The opinion data in this research derive from two sources: mass surveys and profiles of elite attitudes. Each is described below.

Public opinion data

The public opinion data come from Eurobarometer studies provided by the Inter-university Consortium for Political and Social Research (ICPSR), located at the University of Michigan. In 1974, the Commission of the European Communities initiated the series, designed to provide regular monitoring of social and political attitudes of the publics within the EU. These have generated longitudinal and comparative data on controversial issues, including immigration, xenophobia, and race, as well as European integration. They are used here to provide some comparative context for national, ideological, and other polarizations that have evolved over the post-World War II period. Conducted biannually, these surveys consist of batteries of items repeated each year as well as special topics. Since the special issue on immigration and xenophobia in 1988/89, the spring Eurobarometer has consistently included a few questions related to immigration and immigrant groups. Not all questions are asked each year.

Eurobarometers 30, 35, 36, 37, 38, 38.1, 39, 40, 41, 42, 43.1, 44.2, 46, 47.1, 47.2, 48, 49, and 50 were most useful for this study.