A few days ago Walmart, America’s largest employer, announced that it will raise wages for half a million workers. For many of those workers the gains will be small, but the announcement is nonetheless a very big deal, for two reasons. First, there will be spillovers: Walmart is so big that its action will probably lead to raises for millions of workers employed by other companies. Second, and arguably far more important, is what Walmart’s move tells us — namely, that low wages are a political choice, and we can and should choose differently.

Some background: Conservatives — with the backing, I have to admit, of many economists — normally argue that the market for labor is like the market for anything else. The law of supply and demand, they say, determines the level of wages, and the invisible hand of the market will punish anyone who tries to defy this law.

Specifically, this view implies that any attempt to push up wages will either fail or have bad consequences. Setting a minimum wage, it’s claimed, will reduce employment and create a labor surplus, the same way attempts to put floors under the prices of agricultural commodities used to lead to butter mountains, wine lakes and so on. Pressuring employers to pay more, or encouraging workers to organize into unions, will have the same effect.

But labor economists have long questioned this view. Soylent Green — I mean, the labor force — is people. And because workers are people, wages are not, in fact, like the price of butter, and how much workers are paid depends as much on social forces and political power as it does on simple supply and demand.