"Economics Nobel Laureate Gary Becker and Judge Richard Posner", via Jonathan Adler over at Volokh:

An increase in the minimum wage raises the costs of fast foods and other goods produced with large inputs of unskilled labor. Producers adjust both by substituting capital inputs and/or high-skilled labor for minimum-wage workers...

We'd like to think that if Joe is employed doing something for $6.00/hr, and we change the minimum wage to $12.00, that Joe will make twice as much. But, alas, life is not so simple. It pushes back at us.

"Capital inputs" means that they might just decide to automate the supermarket checkout registers instead of paying more for checkers.

Or perhaps instead of hiring Sam, who just got out of jail and is trying to get back on his feet, and will take $6/hour for a while to show he can be trusted -- the manager will hire Dave instead -- who is more qualified and worth about $12 an hour. Before, the owner didn't want to pay for the difference. Now -- why not? Same wage -- he can hire the apparently better-qualified worker and derive a bit of extra value, since he has to pay more anyway.

... and, because the substitutes are more costly (otherwise the substitutions would have been made already), by raising prices. The higher prices reduce the producers' output and thus their demand for labor....

When McDonald's workers are paid a "living wage", you won't be buying many 99 cent cheeseburgers anymore. There goes McDonald's, and all the jobs it offers. Higher wages? No: fewer jobs.

Although some workers benefit — those who were paid the old minimum wage but are worth the new, higher one to the employers — others are pushed into unemployment, the underground economy or crime.

Before, Business X employed five people. Now, they kept just the two most qualified ones, bought some equipment, and laid the other three off. Two people won the "living wage" lottery. Everyone else paid with their jobs. And prices are higher, so poorer customers are also harmed.

"Hooray! We're helping the poor!" writes the press.

Later, the increased numbers of poor will be noted. It will be claimed that we have not done enough, and even more harmful laws will be proposed.