BACKERS of a $15 minimum wage who are celebrating victory in SeaTac now aim to seize the day in Seattle. They do have the political momentum. What they don’t have is a sense of responsibility or of any information on the actual effects of the law they favor.

Earlier in his career, Washington state Treasurer Jim McIntire, Democrat, was the principal investigator for a University of Washington study of the impacts of increases in the minimum wage in 1989 and 1990. The study, funded by the Legislature, found that for every 10 workers who got a raise, one worker lost a job — though many of the laid-off workers were replaced by other ones, typically of higher skill.

The passage of SeaTac Proposition 1 gives that city a minimum wage for some workers 61 percent higher than the $9.32 minimum around it. “That is a pretty dramatic change and could have some significant impacts,” McIntire said recently. “I would counsel the folks in Seattle to see how it goes in SeaTac.”

It is sound advice. The Seattle City Council has approved $100,000 for a study of the issue. The study should find real information on jobs gained and lost, consumer spending and business investment in SeaTac before it reaches a conclusion. Let’s find out what happens in that small city before making a decision for a population 23 times larger.

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Remember also that SeaTac’s measure won’t cover all jobs. Many are inside the airport, protected from competition, which won’t be true of jobs in Seattle. A Seattle proposal that would cover a broader group of workers could have wider negative consequences.