The Seattle City Council on Monday unanimously approved a $15 hourly minimum wage — the highest in the nation.



The ordinance, which phases in the increase over time, passed a committee last week with a few changes. It would take effect next April and allow a sub-minimum wage for teens.



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The ordinance was drafted by an advisory group of labor, business and nonprofit representatives convened by Seattle Mayor Ed Murray. It would phase in wage increases over three to seven years, depending on the size of the business and employee benefits.



The City Council voted 9-0 in front of a sometimes raucous audience that frequently interjected cheers, applause and shouts of "Shame on you!" as the council debated several changes to the measure.



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Seattle's higher minimum wage would surpass San Francisco's minimum of $10.74 an hour.



Washington state also has the highest state minimum wage, at $9.32 an hour.



Some small business owners worry that a higher minimum wage could put them out of business.



Meanwhile, a group called 15 Now led by Socialist Seattle City Council member Kshama Sawant is collecting signatures for a ballot measure that would create an immediate wage hike for large businesses and a three-year phase-in for small business.



"Our victory is not complete, but we have fought until the last day, the last hour, against all the loopholes demanded by business," Sawant said before the council vote. "$15 in Seattle is just the beginning."



-The Associated Press and NBC News staff