Elizabeth Warren, Occupy Wall Street’s favorite senator, is getting another round of praise from liberals for a speech she gave at the AFL-CIO convention on Sept. 8. It’s one more reason the Massachusetts Democrat, just elected in November, is being mentioned as a future presidential contender.

Like a lot of politicians working friendly crowds, Warren was hyperbolic. Wisconsin’s Republican Governor Scott Walker, she said, had “declared war on working families by ripping the guts out of collective-bargaining agreements.” In fact, Walker’s law gives Wisconsin public-sector workers more collective-bargaining privileges than federal employees have.

The comment that has drawn the most approbation was an attack on “the increasing corporate capture of the federal courts.” Citing “a recent study,” (almost certainly this one, in the Minnesota Law Review: http://bit.ly/13VS7MT) she said, “The five conservative justices currently sitting on the Supreme Court are in the top 10 most pro-corporate justices in a half-century — and Justices Alito and Roberts are numbers one and two — the most anti-consumer in this entire time. The Chamber of Commerce is now a major player in the Supreme Court, and its win rate has risen to 70 percent of all cases it supports. Follow this pro-corporate trend to its logical conclusion, and sooner or later you’ll end up with a Supreme Court that functions as a wholly owned subsidiary of big business.”

The study doesn’t tell us what Warren thinks it does, or anything we should care about. It gives equal weight to every vote by a justice, even though decisions plainly vary in importance for businesses, and for everyone else. It ignores decisions that matter a great deal for businesses but don’t have business litigants.

Jonathan Adler, a law professor at Case Western University, notes that the study excludes Massachusetts v. Environmental Protection Agency, one of the two or three most important Supreme Court cases for business of the past decade. The court ruled that the Clean Air Act authorizes the EPA to fight global warming. Because neither named party in the case was a business, the study excludes it.

Adler highlights another problem with the study. Let’s say a court spent years opening many new lines of legal attack on businesses: letting new types of class-action suits go forward, ruling against some business defenses, and so on. Then it slowed down, saying no to some new lines of litigation and yes to only a few, but not shutting down any of the existing lines.

The study’s methodology would find that the justices had become much more pro-business — but the actual legal landscape businesses faced would be worse, not better. It would just be getting worse at a slower rate than before.

Adler believes that something like this story explains a good portion of the results. Evaluating his theory — and evaluating the court’s record on business — requires paying attention to the substance and logic (or lack of logic) of the court’s rulings. It can’t be reduced to numbers.

One of the study’s authors responded to Adler’s criticisms by saying that they had used the best quantitative methods available. It’s as convincing a defense as when drunks explain why they’re looking under a lamppost for their keys.

As for the Chamber of Commerce statistic, it could be telling us about the organization’s litigation strategy as much as about the court’s orientation. It’s an empty number. What percentage does Warren think would be the “right” win rate for the chamber? Anyone who thinks there is a right percentage isn’t thinking properly about law.

This isn’t the first time Warren has cited a dubious study to advance her views about the courts. In June, she complained that more and more judges come from corporate backgrounds. The “study” she cited — which, to its credit, didn’t claim to be any such thing — treated all lawyers in private practice as working for corporations, even if they were actually doing pro bono work or representing civil-rights plaintiffs or something else contrary to her claims. And anyway, there has been a decades-long decline in the percentage of federal judges who come from private practice.

There is an important sense in which the Supreme Court should be pro-business. Justices shouldn’t strain to read laws so that business litigants win their cases. But the protection of commerce, especially from state politicians, was one of the reasons we adopted the Constitution in the first place. Providing that protection has historically been a large part of the court’s work.

It hasn’t been in recent decades. The idea has gone so out of fashion that saying that the court is pro-business is nowadays an accusation. But that accusation, especially as voiced by Senator Warren, is unfounded.