Seattle City Councilmember Kshama Sawant is raising concerns about research into the city’s landmark minimum-wage law, prompting a University of Washington team to defend its work.

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Seattle City Councilmember Kshama Sawant is raising concerns about city-commissioned research into Seattle’s landmark minimum-wage law and about public comments by one of the University of Washington professors leading the effort.

Professor Jacob Vigdor and other members of the UW team, who in July published a preliminary report on the impact of the law, are defending their work and saying they don’t control how their comments are presented in the media.

The report said Seattle’s labor market thrived after the city became the first major metropolis in the country to enact a law setting its minimum wage on a multiyear path to $15 per hour. It said much of that success can be attributed to trends separate from the law itself, such as the growth of Seattle’s tech sector.

Why all the fuss about a group of number crunchers and their study, which is scheduled to continue for five years? People across the country — including pundits and activists on both sides of the political spectrum — are closely watching what happens in Seattleas they debate whether to raise minimum wages in their own cities and states, and nationwide.

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“I’m not only concerned that we’re in danger of drawing erroneous conclusions about Seattle’s minimum-wage increase — I’m concerned about the consequences that could have on the nationwide fight for $15 (per hour),” said Sawant, who holds a doctorate in economics and was an instructor at Seattle Central College before winning office.

In a letter addressed to Vigdor on Tuesday, Sawant questioned the study’s methodology and Vigdor’s objectivity. On the first issue, she attacked the “synthetic Seattle” statistical model that the UW team used to prepare the report.

To try to isolate the impact of the minimum-wage law from other conditions, the team aggregated ZIP codes from outside the city that had previously shown data and trends similar to ZIP codes inside the city. The team compared what happened in real Seattle from June 2014 through December 2015 to what happened in synthetic Seattle.

“I have strong reservations about the relevance of a model built on geographically and demographically distant ZIP codes,” rather than on ZIP codes just outside the city’s borders, Sawant wrote.

She faulted the researchers on other academic grounds, as well, saying they failed to adjust for seasonality and to include chain businesses in the study, for example.

Sawant also went after Vigdor’s comments in the media.

“Wages, jobs, hours worked and net business openings all increased in Seattle. Yet you chose to emphasize to the press that employment rates and hours worked went down compared to the fictional synthetic Seattle,” she wrote. “It is professionally irresponsible to draw such a conclusion from the data at this time.”

To conclude, Sawant wrote, “Your methodological shortcomings and ideological editorializing undermine the credibility of the report.”

In a letter replying to Sawant on Tuesday, Vigdor and 10 other UW researchers, including several professors, said their work is a collective project.

“The research products generated by the minimum-wage study team are the work of all team members and not one member,” they wrote. “The entire team has participated in discussion around research design, analysis, interpretation and presentation of results. We have taken great care to discuss where we find the evidence most compelling and where we are most uncertain. We believe our report reflects this care and caution.”

The synthetic Seattle approach has been used before for minimum-wage research and is a good approach for various reasons, the team wrote. And besides, the July report had an appendix with the approach Sawant prefers.

“None of the conclusions reached in our report are contradicted” by the use of that alternate approach, the team’s letter said.

The researchers admitted to some methodological challenges. But, they wrote, “In the end, we believe that every question or criticism raised in your letter reflects information fully disclosed and discussed in the report itself.”

With regard to Vigdor’s objectivity and comments, the team noted, “Our work product is a public document, subject to partisan interpretation,” and said parts of the report have been used to promote both positive and negative views of Seattle’s law.

The researchers said their comments in the media can be taken out of context. But they said the stories about the July report that have been most misleading have been those written by people who didn’t speak to the team.

In an interview, Vigdor insisted that he’s playing it straight.

“We have no ideological commitment,” he said. “We may appear as though we have some ideological slant because we’re not reliably agreeing with anybody.”

The former Duke University professor is an adjunct fellow at the conservative Manhattan Institute and a onetime visiting scholar at the right-leaning American Enterprise Institute. He said that he recently spoke out against American Enterprise Institute scholar Mark Perry’s criticism of Seattle’s minimum-wage law.

“Our entire team is troubled by the high and persistent degree of income inequality in the United States and believe our nation has a moral responsibility to ensure that the fruits of our prosperity are shared equitably,” the UW letter said.

“We are committed to producing objective and rigorous research, however, regardless of our individual preferences or concerns.”