Conservative Vote Probabilities: An Easier Method for the Analysis of Roll Call Data

Abstract

We propose a new roll-call scaling method based on OLS which is easier to implement and understand than previous methods and also produces directly interpretable estimates. This measure, Conservative Vote Probability (CVP), indicates the probability that an individual legislator votes “conservatively” relative to the median legislator. CVP is a flexible non-parametric statistical technique that requires no complicated assumptions but still produces legislator scalings that correlate with previous roll call methods at extremely high levels. In this paper we introduce the methodology behind CVP and offer several substantive examples to demonstrate its efficacy as an easier, more accessible alternative to previous roll call methods.