Wijbrandt H Van SchuurWijbrandt H. van Schuur is associate professor at the Faculty of Behavioral and Social Sciences of the University of Groningen, The Netherlands. He is interested in measurement models and has taught measurement and scaling models in Groningen and at he Essex Summer School in Social Science Data Analysis. He has developed an ordinal unidimensional unfolding model and a model for the ordinal circumplex (for the first see Political Analysis, 1993, and Applied Psychological Measurement, 1994; and for the second, Essays in item response theory: Lecture notes in statistics, Vol. 157, 2001). His main substantive research interest is in the measurement of political knowledge (e.g. Acta Politica 2000), and, in collaboration with the Documentation Centre Dutch Political Parties, the study of party membership (e.g. Research in Political Sociology, Vol. 18, 2010).