Liberals are living in a utopia that if you raise the minimum wage to $15/hour, then everyone will go up proportionally, prices will stay the same, and everything is great. Sounds wonderful, but that's not how the world works.
Companies are not going to lose profit margin b/c of their kind hearts. I wish it was true, but their not. Can many afford to, yes? Will they, no.
There are five things to remember, wages, # of jobs, location, government assistance, and purchase power. I've seen many make arguments about one or two of these things, but they are all interlinked. And there is no way to make all four go up or stay the same. Governments have tried, and they've all failed. They're are going to be losers, no matter how you look at it.
Location is probably the easiest thing to tackle, but also one of the hardest to politically explain b/c it makes things complicated and the American public likes things simple. The problem with a 'one size fits all' legislation is the country, like its citzens, is not all one size. If you instituted a $15/hour minimum in Northern Virginia (NOVA), it would do very little since a cashier at McD's already makes that. Its what the market demands. But in Jackson, Mississippi, that's not the case. $15/hour is an easy selling position, but saying it works here so it will work everywhere the same is not the case.
Let's raise the minimum wage to $15/hour and essentially double the lowest paid worker. So in the McD's example (Jackson MS for this example, not NOVA b/c nothing happens in NOVA), we've increase every cashier from 15K to 30K for the year. And every cook 20K to 30K (assuming they made $10/hour). Now out of the kindness of the owner's heart, he/she will eat the profits, right? Wrong. The owner has 3 options. Have current employees work more and hire less, automate and hire less, and/or raise prices. We know its going to be a combination of the three.
You can't just raise prices to cover the cost. Customers are too sensitive to prices rising too quickly. Doing so will run off your customer base. Its ends up being a combination of the three.
So what happens at the macro level to all our issues. Wages, they go up; # of jobs go down; amount of people on assistance goes down, but amount needed for ones on assistance goes up; purchase power varies depending on where you are on the wage ladder; prices go up, but not all at once, its gradual. And as prices go up, the purchase power for many goes down. So there is a time issue here.
The idea that if you move it to $15/hour it will be good forever is a fallacy. You will eventually have to move it to $30/hour and so on and so on.