Thomas Däubler, Kenneth Benoit
The empirical determinants of manifesto content

3rd Annual General Conference of the European Political Science Association, Barcelona, 20. bis 22. Juni 2013

Party manifestos form the largest source of textual data for estimating party policy positions, typically based on methods that assume that longer manifestos with more units of text provide more confident estimates. Despite using them extensively for nearly three decades, however, we know little to nothing about what explains why either the overall length of manifestos or their scope of issue coverage varies so highly across parties, elections, and contexts. Here, we critically test the notion that political context affects overall length and manifesto content. We use multi-level modeling to predict manifesto length and issue scope in a large number of coded party manifestos covering the post-war period. Our findings indicate that manifesto length and the scope of issue coverage can be largely explained by a combination of political variables related to party size, policy orientation, as well as election-specific factors related to political competition and the timing of elections.