Measuring Political Positions from Legislative Speech

Existing approaches to measuring political disagreement from text data perform poorly except when applied to narrowly selected texts discussing the same issue and written in the same style. We demonstrate the first viable approach to scaling the entire speech corpus of a legislature, producing valid legislator-specific scores as well as extensive information about the evolution of speech polarization and politically loaded language. In the Irish Dail, we show that the dominant dimension of speech variation is government-opposition, with ministers more extreme on this dimension than backbenchers. In the US Senate, we estimate a dimension that has moderate within-party correlations with scales based on roll-call votes and campaign donation patterns, however we observe greater overlap across parties in speech positions than roll-call positions and partisan polarization in speeches varies more clearly in response to major political events.