Sandy Baum, an economist at Skidmore College whose research laid the groundwork for the proposed rules, said the department's regulations set the bar very low but the judge had created an impossible threshold because "there is no one right measure, " she said.

WSJ: For-Profit Colleges Score Victory With Judge's Ruling

This created a peculiar incentive: at least one study suggests that firms just below the threshold began disbursing unusual amounts of cash to shareholders and making fewer investments.

ECONOMIST: Economics focus