As the New York Times documents, a Lee Epstein/Landes/Posner study found that the Roberts court ruled in favor of business 61% of the time. Does that mean that it's pro-business?
Hardly. Remember that the Court is a reviewing court. All a 61% "pro-business" rate tells us is that the Supreme Court is more pro-business (or less anti-business) than the courts it is reviewing. Thus any of the following scenarios may be true:
The Supreme Court is pro-business;
Lower courts are anti-business, and the Supreme Court is neutral; or
Lower courts are anti-business, and the Supreme Court is also anti-business, but not as anti-business as the lower courts.
For example, a perfectly neutral Supreme Court might rule in favor of business 80% of the time out of the cases that were on its docket. We simply can't know if the Supreme Court's rulings are "biased" from the quantitative count unless we also make a qualitative judgment how often business should win in front of the Supreme Court; Adam Liptak seems to assume that that number should be somewhere in the 50% range (or even lower in the instance of employment discrimination cases, when he points out accusingly that the Rehnquist court ruled in favor of plaintiffs 64% of the time), but there's no reason that should necessarily be so.
This is before we get to the problem I have frequently raised in the past of what constitutes a "pro-business" decision. For example, Exxon Shipping technically "won" the Exxon Shipping v. Baker case by having its punitive damages reduced from the excessive amount imposed by the Ninth Circuit--but the decision loosened the circumstances in which punitive damages could be imposed, and was hardly a plus for business.
The fact that the number of business cases on the docket has increased from 21% under Rehnquist to 27% under Roberts similarly only demonstrates relative preferences; I predicted as much in 2005, simply because of Rehnquist's apparent distaste for the Supreme Court getting involved in business cases. The increase is significant, but hardly evidence of a pro-business bias; virtually every Supreme Court practitioner in Washington, DC, can point to a cert petition in a business case that they felt was unjustly denied.
See earlier Jonathan Adler.