The University of Washington is studying the impacts of Seattle's minimum wage ordinance. They recently released a paper that describes the methodology for their study and provides preliminary estimates of the ordinance's impact on prices.

The price information is inconclusive, to say the least. There are many caveats:

• They may not adequately describe firm responses in the long run.
• They cover only the initial increase from $9.47 to $11.
• Their baseline price data collection occurred in March 2015, which "may be close enough to the April 1 minimum wage increase that it already incorporates anticipatory responses to a policy change that had been announced several months before."
• "As effects of the minimum wage may only be felt after a time lag, owing to delays in business adaptation involving capital investment, and also to the stepped nature of the increase to $15 in Seattle . . . the complete impact of the $15 minimum wage in Seattle may not be known for nearly a decade."

Their price survey included grocery stores and other retail. (And one-fifth of the businesses sampled were restaurants.) They found "at most small positive effects on prices." But, at restaurants, prices increased by an average of 7.7 percent, suggesting "a concentration of price effects in the restaurant industry." (They note, however, that "it is unclear whether this increase can be fully or even partially attributed to the minimum wage itself.")

KPLU has a story on the preliminary study. It notes that Jacob Vigdor, a professor at UW who is working on the project, "said his team didn’t collect that much restaurant data outside the city, making it a bit hard to draw conclusions."

According to the paper, future work will include:

• Analysis of employment and earnings data.
• The impacts of the higher minimum wage on means-tested program participation and benefits.
• Comparison with control regions.
• Employer surveys.
• A longitudinal, qualitative study of 53 low-wage workers with children.

Additionally, the research will look at Chicago's minimum wage increase and state-level minimum wage increases that occurred between 2006 and 2008.