The Ins and Outs of Measuring Populism with Expert Surveys

In the last years, the study of populist parties has matured in terms of our theoretical understanding of populism as well as the identification of the causes of populist party success. One area where populism research lags behind is data collection. This has to do in part with the fact that our data has not kept pace with the theoretical understanding of populism. While scholars of populism have become increasingly successful at measuring populism the demand side, measurement of the supply-side of populism remains piecemeal as it relies on costly textual analyses of populist discourse. With this contribution we introduce the Political Parties and Populism Expert Survey (POPPA) dataset. Fielded in the spring of 2018, the survey contains over 280 parties from over 31 European countries based on the assessments of over 300 experts. Experts were asked to judge all relevant parties in the these countries’ party systems on various dimensions of populism, on party organization, and on attaching ideological dimensions. This paper we has two purposes. First, we examine whether it is possible to measure populism using expert surveys. To ensure external validity, we cross-validate the POPPA estimates with other supply-side measures of party positions and populism. To ensure internal validity as well as reliability, we examine expert coherence and agreement. Second, we explore the extent that this dataset can bring new insights into the study of supply-side populism. A distinct advantage of using expert surveys is that we have a populist measure for all parties in all party systems. In light of this, we examine and compare populism across several ideological dimensions, while we also explore attributes that are often associated with populism, such as personalization and and a lack of internal party democracy. In the process we attempt to map and compare populist parties across the European context.