It won't. Econ 101. It's been proven thousands of times all over the world that you can't vote yourself prosperity. The supply curve still operates the same, around the world, no matter what a city council may believe.
Every time someone makes an argument for this, ask yourself, why not $20? Why not $25? Ask yourself, how did central planning work in the old USSR? How has it worked since it was ended in China?
I ask myself as an employee, am I generating enough revenue to justify my salary? Because there is nothing else this comes down to, and if employees are not generating that, there are three choices: either you're fired, your hours are cut back, or the business closes. There literally are no other choices.
So, what's employment in Seattle today?
Lower than the national average. That's a good starting point for this kind of project. Historically, higher minimum wages result in a rise in unemployment. That's what is expected from the supply curve. Let's see what happens in five years. I expect it to be up about 2-3 points and I expect city tax revenues will be
down. Good luck to the poor, who will be the first and the worst affected by this. If I turn out to be wrong I will happily admit it.