Using confidential payroll data from the Washington Employment Security Department, the researchers compare employment, hours and wages of workers in Seattle and various other parts of Washington both before and after Seattle began raising its minimum wage. They argue that Seattle’s minimum wage increase reduced the total hours worked by Seattle’s low-wage workforce by about 9 percent. They also contend that the increase raised low-wage workers’ wages by only about 3 percent, implying that the costs of this wage hike outweighed its benefits for these workers.

But the idea that raising the minimum wage has a much larger effect on hours than on wages strains credulity, especially since, as economists Ben Zipperer and John Schmitt have noted, Seattle’s increase “is within the range of increases that other research has found to have had little to no effect on employment.” The study also finds that the minimum wage caused large employment and hours gains in higher-wage jobs, which suggests that its “methodology fails to account properly for the booming Seattle labor market during the period studied.” It’s not entirely clear why the University of Washington team gets such a weird result — since their data isn’t public, we can’t check it — but it’s worth noting at least two important issues with their study.