Published online by Cambridge University Press: 21 December 2015
Well-established methods exist for measuring party positions, but reliable means for estimating intra-party preferences remain underdeveloped. While most efforts focus on estimating the ideal points of individual legislators based on inductive scaling of roll call votes, this data suffers from two problems: selection bias due to unrecorded votes and strong party discipline, which tends to make voting a strategic rather than a sincere indication of preferences. By contrast, legislative speeches are relatively unconstrained, as party leaders are less likely to punish MPs for speaking freely as long as they vote with the party line. Yet, the differences between roll call estimations and text scalings remain essentially unexplored, despite the growing application of statistical analysis of textual data to measure policy preferences. Our paper addresses this lacuna by exploiting a rich feature of the Swiss legislature: on most bills, legislators both vote and speak many times. Using this data, we compare text-based scaling of ideal points to vote-based scaling from a crucial piece of energy legislation. Our findings confirm that text scalings reveal larger intra-party differences than roll calls. Using regression models, we further explain the differences between roll call and text scalings by attributing differences to constituency-level preferences for energy policy.
Daniel Schwarz is postdoctoral research fellow in the Center of Competence for Public Management, University of Bern, Schanzeneckstrasse 1, 3001 Bern, Switzerland, and Department of Methodology, London School of Economics and Political Science, Columbia House, Houghton Street, London WC2A 2AE, UK (firstname.lastname@example.org). Denise Traber is postdoctoral researcher in the Department of Political Science, University of Zurich, Affolternstrasse 56, 8050 Zurich, Switzerland (email@example.com). Kenneth Benoit is Professor of Political Science Research Methodology in the Department of Methodology, London School of Economics and Political Science, Columbia House, Houghton Street, London WC2A 2AE, UK, and Department of Political Science, Trinity College, 3 College Green, Dublin 2, Ireland (firstname.lastname@example.org). This research was supported by the European Research Council grant ERC-2011-StG 283794-QUANTESS and the Swiss National Science Foundation Fellowship grant PA00P1_134188.