The judicial common space

To say that positive political theory (PPT) scholarship on the hierarchy of justice is theory rich and data poor is to make a rather uncontroversial claim. For over a decade now, scholars have offered intriguing theoretical accounts aimed at understanding why lower courts defy (comply with) higher courts. But only rarely do they subject the accounts to rigorous empirical interrogation. The chief obstacle, it seems, is the lack of a reliable and valid measurement strategy for placing judges of lower courts and justices of higher courts in the same policy space. Without such a strategy, we can systematically test few, if any, hypotheses flowing from PPT models of the judicial hierarchy. With such an approach not only can we investigate the implications of these models, we can assess many others flowing from the larger PPT program on judging, as well. It is to the challenge of scaling judges and justices (as well as legislatures and executives) that we turn in this article. We begin by explicating our measurement strategy, and then by explaining its advantages over previous efforts. Next we explore the results of our approach and provide a descriptive look at data it yields: a "Judicial Common Space" (JCS) score for all justices and judges appointed since 1953. The last section offers three applications designed to shore up the suitability and adaptability of the JCS for a range of positive projects on the courts.