Studying policy congruence between citizens and their representatives in the European Parliament (EP) necessitates information on the position of various political actors: voters, national political parties, and candidates to the EP or supranational political parties. Although high quality comparative studies have been designed to overcome problems caused by cross-nationality, there are still some important discrepancies that deserve attention. All measures come with their merits and limitations.
To what extent are these measures comparable and compatible? Choices among different measures depend on the specific research question. We discuss the theoretical and methodological trade-offs involved, as well as the differences and similarities of various measurement techniques used in the literature. The paper compares political actors’ policy positions on the basis of different measures and evaluates compatibility using concordance correlation coefficient. We conclude with remarks regarding measure suitability for specific types of research puzzles and the levels of compatibility among them.
