The Most Dangerous Justice Rides Again: Revisiting the Power Pageant of the Justices

Abstract:     
Who is the most powerful Supreme Court Justice? In 1996 we measured voting power on the Court according to each Justice's ability to form five-member coalitions. From the set of all coalitions formed by the Court during its 1994 and 1995 Terms, we developed a generalized Banzhaf index of the Justices' relative strength. Generally speaking, participating in a greater number of unique coalitions translates into greater judicial voting power. To supplement the small number of decisions then available, we derived hypothetical five-Justice coalitions from the intersections of actually observed coalitions involving more than five members. Professor Lynn Baker contested our model, favoring instead an additive measure based on the number of times each Justice participated in any winning coalition.

This Article stages a new Power Pageant of the Justices in light of the cases decided by the Court since 1996. For more than seven Terms, the Court has retained the same personnel. This stability provides a unique opportunity to test competing measures of judicial voting power. We hypothesized in 1996 that a larger set of cases might obviate the need to resort to inferred coalitions. Analysis of this larger data set in fact undermines the validity of both our measure and that of Professor Baker over the long run. We conclude that there are three different measures of voting power each reflecting a different aspect of judicial power.

Keywords: Banzhaf index, voting power, Supreme Court, Anthony Kennedy

JEL Classifications: C78, D72

Accepted Paper Series