Seattle Minimum Wage Study Has Serious Flaws

“Remember the story from last week about how the new Seattle minimum wage law was hurting workers?” writes Slashdot reader PopeRatzo. “Well, it turns out that there are some problems with the study’s methodology.” The Washington Post reports:

First, their data exclude workers at businesses that have more than one location; in other words, while workers at a standalone mom-and-pop restaurant show up in their results, workers at Starbucks and McDonald’s don’t. Almost 40 percent of workers in Washington state work at multi-location businesses, and since Seattle’s minimum wage increase has been larger at large businesses than at small ones — right now, a worker at a company with more than 500 employees is guaranteed $13.50 an hour, while a worker at a company with fewer than 500 employees is guaranteed only $11 an hour — these workers’ exclusion from the study’s results is an especially germane problem (note that low-wage workers in Seattle have had an incentive to switch from small firms to large firms since the minimum wage started rising).
In earlier work, in fact, the University of Washington team’s results were different depending on whether these workers were included in their analysis; including them made the effects of the minimum wage look more positive. Second, the University of Washington team does not present enough data for us to assess the validity of its “synthetic control” in Washington — that is, the set of areas to which they compare the results they observe in Seattle. The Seattle labor market is not necessarily comparable to other labor markets in the state, and given some of the researchers’ implausible results, it’s hard to believe the comparison group they chose is an appropriate one.
Suggesting Seattle’s booming labor market may have skewed the study’s results, two nonpartisan economists concluded it “suffers from a number of data and methodological problems that bias the study in the direction of finding job loss, even where there may have been no job loss at all.” And the Washington Post also notes the researchers findings are suspiciously “out of step with a large body of research,” including another study from U.C. Berkeley researchers [PDF] which determined Seattle’s wage increase “is having its intended effect.”

Read more of this story at Slashdot.