Intra-Party Preference Heterogeneity and Faction Membership in the 15th German Bundestag: A Computational Text Analysis of Parliamentary Speeches

In a broad range of research in comparative politics, political parties are conceptualised as unitary actors with consistent preferences. We depart from this sometimes accurate, at other times overly strong assumption by studying patterns of intra-party heterogeneity of preferences within parliamentary parties in the German Bundestag from 2002-05. For this purpose, we use the Wordscores method, a form of computational text analysis, to estimate policy positions of 453 individual legislators based on plenary speeches. We then study the link between intra-party faction membership and expressed policy positions. We find that there is a limited, but consistent effect of intra-party factionalism in the German Bundestag. According to random effects ANOVA, faction membership determines about 3 per cent of the variance of positions on economic policy in the present study.