Who are the Activist Judges?

A Yale Law School professor tried to measure judicial activism on the Supreme Court. The question is what measure to use? While nothing perfect came to mind, he figured the number of times a justice voted to strike down a law passed by Congress was a reasonable measure. "Until 1991, the court struck down an average of about one Congressional statute every two years. Between 1791 and 1858, only two such invalidations occurred...Since the Supreme Court assumed its current composition in 1994, by our count it has upheld or struck down 64 Congressional provisions." Here's how often the justices voted to strike down the law in each of these 64 cases.

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%

By this measure, the conservative justices are the most activist. While this might not be a good measure, it does question the conservative claims that liberal activists are ruling from the bench. From this It seems that conservative justices are far more likely to strike down laws passed by an elected (and during this time Republican) Congress. I guess that's why Congress is so upset about it. One thing that strikes me about the figures, I'm not sure why they didn't look at all decisions, not just these 64, surely there must of have many times when the Court voted to retain the law and had some dissenters who wanted to strike it down.