The mayor of Seattle announced Thursday that he'd developed a plan for a $15 minimum wage that had wide backing from the city's lawmakers, labor leaders and business community.

The proposal unveiled by Mayor Ed Murray would gradually raise the city's minimum wage from $9.32 to $15 over the course of three to seven years, making it the highest city wage floor in the nation. The speed of the hike for individual employers would depend upon how many workers they have and the value of the non-wage benefits they offer.

“Once again Seattle has chosen to collaborate and Seattle workers are going to get a raise,” Murray said at a Thursday news conference, according to the Seattle Times.

Murray's plan is just a proposal for now, and it would require the city council to write legislation and pass it. But the mayor said the plan enjoyed broad support from the commission he'd tasked with developing it, with 21 members of the 24-member committee having agreed to it.

The proposal is least forgiving for large businesses with more than 500 workers, which will have to reach the new $15 minimum by 2017 if they don't give workers tips or health coverage; if they do, they'll be given another year to reach $15. Businesses with fewer than 500 workers will have until either 2019 or 2021 to hit $15, depending on the benefits they offer.

After reaching $15, the minimum wage would rise by 2.4 percent each year to adjust for inflation.

The long lead time reflects a compromise. As PBS NewsHour has reported in an ongoing series, some Seattle business owners have opposed the wage hike, saying they would be forced to cut hours for workers, raise prices on consumers or both. The plan announced by Murray would give small businesses in particular several years before having to cover the full cost of the increase.

As Congress has stalled on the federal minimum wage, cities and states around the country have moved to raise their own wage floors with large public support. Washington and its municipalities have been particularly aggressive. Washington currently has the highest state minimum wage in the nation at $9.32 per hour, and the city of SeaTac, a Seattle suburb that includes Seattle-Tacoma International Airport, recently passed a $15 minimum wage that applies to airport service workers.