Studying Judicial Disagreement Quantitatively: The Case of Judges on the UK Supreme Court

This paper reports on an ongoing study (joint with Professor TT Arvind) of why, in what ways, and with what consequences judges of the UK Supreme Court disagree. It rejects the starting point, common in the US judicial politics literature, that judicial disagreement is 'political' in the sense that it can be adequately captured along a classical liberal–conservative. Instead it proceeds from the assumption that judicial disagreement on the UK Supreme Court is 'doctrinal', and that if such disagreement is to be measured quantitatively, then it must be measured in ways that capture this doctrinal dimension. We take Harlow and Rawlings' distinction between red-light and green-light approaches towards state decisions as a basis for constructing a doctrinal scale of judicial ideal points. Empirically, such a dimension better captures patterns of decision-making than a classical liberal–conservative scale. The present paper goes beyond our earlier published work ("Legal Ideology, Legal Doctrine and the UK's Top Judges", Public Law, July 2016: 418–436) by presenting dynamic estimates of UK Supreme Court judges' ideal points. Preliminary findings from dynamic models suggests distinct eras of consensus and dissensus, with the Supreme Court currently witnessing a period of divergence in judicial attitudes.