What is an Activist Judge?

Gerwitz and Golder want to define "judicial activism" as a function of votes to strike down legislations. As they note, it's not necessarily a bad thing, but it's one non-partisan way to measure it. What I'd like to see is an analysis that differentiated between striking down legislation produced by a Congress of one's own party and that produced by a Congress of the other party. This court has sat through mostly Republican dominated Congresses, though, so that's not a terribly important distinction in the short term.

Thomas 65.63 %
Kennedy 64.06 %
Scalia 56.25 %
Rehnquist 46.88 %
O’Connor 46.77 %
Souter 42.19 %
Stevens 39.34 %
Ginsburg 39.06 %
Breyer 28.13 %