Menu prices are up 21 percent and you don't have to tip at Ivar's Salmon House on Seattle's Lake Union after the restaurant decided to institute the city's $15-an-hour minimum wage two years ahead of schedule. It is staff, not diners, who feel the real difference, with wages as much as 60 percent higher than before. One waitress is saving for accounting classes and finding it easier to take weekend vacations, while another server is using the added pay to cover increased rent.

Seattle's law, adopted last year after a strong push from labor and grassroots activists, bumped the city's minimum wage to $11 beginning April 1, above Washington state's highest-in-the-nation $9.47. Scheduled increases that depend on business size and benefits will bring the minimum to $15 within four years for large businesses and seven years for smaller ones.

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There's little data yet on how the law's working.

Seattle, Washington. Lightvision LLC | Getty Images

"To the extent that we can look at macro patterns, we're not seeing a problem," said Seattle Mayor Ed Murray.

As Washington, D.C., and other cities consider following Seattle, San Francisco and Los Angeles in phasing in a $15-an-hour minimum wage, Ivar's approach, adopted in April, offers lessons in how some businesses might adapt. Ivar's Seafood Restaurants President Bob Donegan decided to raise prices, tell customers that they don't need to tip, and parcel the added revenue among the hourly staff.

For some of the restaurant's lesser paid workers - including bussers and dishwashers - that's meant as much as 60 percent more. Revenue has soared, supportive customers are leaving additional tips even though they don't need to, and servers and bartenders are on pace to increase their annual pay by thousands, with wages for a few of the best compensated approaching $80,000 a year.

"It's been a surprise," Donegan said. "The customers seem to like it, the employees seem to like it, and it seems to be working, at least in this location."

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Rochelle Hann, 25, is a second-generation worker at Ivar's. Like her mom, she has performed a variety of roles, including serving, bookkeeping and even dressing up as a giant clam. If she keeps working 30 hours a week, her annual pay will jump about $12,000 - money she's socking away for accounting classes at a community college.

"Before, I felt like it was maybe not quite paycheck-to-paycheck, but now I don't even have to worry about it," she said. "I just went away for the weekend, and it was an easy expense."

Brett Richards, a 50-year-old singer and guitarist, has worked 25 years in food service, including the past eight at Ivar's. Before, he made minimum wage, plus tips. Now, he gets $15 an hour, plus a share of the 21 percent menu price increase, plus any additional tips customers leave. He expects to make almost $7,000 more this year, money that's helping him with his increased rent and with taking his kids out to eat a little more often.