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Estimating Party Positions across Countries and Time—A Dynamic Latent Variable Model for Manifesto Data

  • Thomas König (a1), Moritz Marbach (a2) and Moritz Osnabrügge (a3)

This article presents a new method for estimating positions of political parties across country- and time-specific contexts by introducing a latent variable model for manifesto data. We estimate latent positions and exploit bridge observations to make the scales comparable. We also incorporate expert survey data as prior information in the estimation process to avoid ex post facto interpretation of the latent space. To illustrate the empirical contribution of our method, we estimate the left-right positions of 388 parties competing in 238 elections across twenty-five countries and over sixty years. Compared to the puzzling volatility of existing estimates, we find that parties more modestly change their left-right positions over time. We also show that estimates without country- and time-specific bias parameters risk serious, systematic bias in about two-thirds of our data. This suggests that researchers should carefully consider the comparability of party positions across countries and/or time.

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Authors' note: For helpful comments and suggestions, we thank two anonymous reviewers, R. Michael Alvarez, Meghan Helsel, Carlo Horz, Dirk Junge, Sebastian Köhler, James Lo, Bernd Luig, Andrew D. Martin, Sven-Oliver Proksch, Zeynep Somer-Topcu, and the participants of the Finding Thetas Conference 2012 in Bern. Sophie Mathes provided excellent research assistance. All errors remain our responsibility. Replication data are available at (König, Marbach, and Osnabrügge 2013). Supplementary materials for this article are available on the Political Analysis Web site.

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