First, a few facts. Although the national minimum wage was raised a few years ago, it’s still very low by historical standards, having consistently lagged behind both inflation and average wage levels. Who gets paid this low minimum? By and large, it’s the man or woman behind the cash register: almost 60 percent of U.S. minimum-wage workers are in either food service or sales. This means, by the way, that one argument often invoked against any attempt to raise wages — the threat of foreign competition — won’t wash here: Americans won’t drive to China to pick up their burgers and fries.

Still, even if international competition isn’t an issue, can we really help workers simply by legislating a higher wage? Doesn’t that violate the law of supply and demand? Won’t the market gods smite us with their invisible hand? The answer is that we have a lot of evidence on what happens when you raise the minimum wage. And the evidence is overwhelmingly positive: hiking the minimum wage has little or no adverse effect on employment, while significantly increasing workers’ earnings.

It’s important to understand how good this evidence is. Normally, economic analysis is handicapped by the absence of controlled experiments. For example, we can look at what happened to the U.S. economy after the Obama stimulus went into effect, but we can’t observe an alternative universe in which there was no stimulus, and compare the results.