In my last post, I discussed the measure I have proposed in my article for the judicial ideologies of federal appellate and district judges. That leads to the question: how do we know if my measure is “good?” Anyone can make up a bunch of numbers and formulas and declare their measure to be better than existing ones. How can it be said with any certainty that one measure of ideology is quantitatively or qualitatively better than another? That is one of the trickier questions in empirical legal studies of federal courts.
Consider the very interesting and valuable studyby Michael Heise and Gregory Sisk of judicial ideology in religious liberty cases published in the Northwestern University Law Review a few years ago. The study found, consistent with prior research, that ideology had a modest correlation with outcomes in religious liberty cases. How was ideology measured? Using Common Space Scores. What if the Common Space Scores were actually a poor measure of judicial ideology and votes in religious liberty cases were actually a “better” indicator of a judge’s ideology? How would we know? Heise and Sisk chose to use Common Space Scores even while noting in detail the potential problems with the Scores. Of course, Heise and Sisk did so in part because they framed their study as part of a response to the firestorm created by an article by Lee Epstein and Gary King attacking empirical legal studies by legal academics. The types of inferences that can be drawn from the Heise and Sisk study would change dramatically if Common Space Scores were not strong indicators of judicial ideology. Read More