The Berkeley study, however, looked exclusively at the restaurant industry. That has been a
common practice in minimum-wage research, because the industry is one of the
largest employers of low-wage workers. But the University of Washington study suggests a possible flaw in that approach: That research, too, found essentially no job losses in the restaurant sector as a result of the city’s minimum wage hike.
That suggests that studies that focused on the restaurant industry might have missed larger effects in other sectors. (Michael Reich, one of the authors of the Berkeley study, said he was confident in his findings. Bernstein said focusing on restaurants, especially fast food, was a widely accepted approach that was well grounded in economic theory.)