In today's Los Angeles Times, Ed Whelan critiques the Miles/Sunstein study examining "judicial activism" on the Supreme Court. First, Whelan objects to focusing on review of agency decisions, as opposed to rulings on the constitutionality of state or federal statutes, because only in the latter case is the result of a court decision effectively immune from revision through the democratic process (or even by additional administrative action). Whelan also thinks there are methodological probems with the Miles/Sunstein analysis:

They classify rulings as "restrained" or "activist" without regard to any qualitatitive assessment of whether the ruling is correct. They implicitly presume that the work product of federal bureaucrats is politically neutral. . . . If an agency shows a bias in a particular direction, a neutral judge's decisions overruling that agency's actions would of course show a pattern in the opposite direction. Thus, if federal agencies, captured by career bureaucrats, are prone to err in a liberal direction, the "Partisan Voting Award" that Miles and Sunstein would confer on Justice Thomas instead belongs to the agencies.

Miles' and Sunstein's statistics are also skewed by the fact that they cover the period from 1989 through 2005. Justices Ginsburg and Breyer were not on the court in the early years of that period, when the court was reviewing agency decisions from Republican administrations that account for about a third of the total cases. The relative partisanship that Miles and Sunstein find in Ginsburg's and Breyer's votes would surely have been much higher if Miles and Sunstein had used the same set of cases for all justices.

It seems to me that these critiques significantly undermine the force of the Miles/Sunstein analysis.

UPDATE: Patterico offers additional critiques of the Miles/Sunstein analysis here.