An Expert-Sourced Measure of Judicial Ideology

Abstract This article develops the first dynamic method for systematically estimating the ideologies and other traits of nearly the entire federal judiciary. The Jurist-Derived Judicial Ideology Scores (JuDJIS) method derives from computational text analysis of over 20,000 written evaluations by a representative sample of tens of thousands of jurists as part of an ongoing, systematic survey initiative begun in 1985. The resulting data constitute not only the first such comprehensive federal-court measure that is dynamic, but also the only such measure that is based on judging, and the only such measure that is potentially multi-dimensional. The results of empirical validity tests reflect these advantages. Validation on a set of several-thousand appellate decisions indicates that the ideology estimates predict outcomes significantly more accurately than the existing appellate measures, such as the Judicial Common Space. In addition to informing theoretical debates about the nature of judicial ideology and decision-making, the JuDJIS initiative might lead courts scholars to revisit some of the lower-court research findings of the last two decades, which are generally based on static, non-judicial models. Perhaps most importantly, this method could foster breakthroughs in courts research that, until now, were impossible due to data limitations.