Labor Force Participation Rate Among Men Aged 25 to 54, 2004-2014

It's said again and again that immigrants do not take jobs from natives. Here’s National Journal, reporting just last year, under the headline "Left and Right Agree: Immigrants Don't Take American Jobs":

That immigrants take the jobs of American-born citizens is “something that virtually no learned person believes in,” Alex Nowrasteh, an immigration expert at the libertarian Cato Institute, said at a Thursday panel. “It’s sort of a silly thing.” Most economists don’t find immigrants driving down wages or jobs, the Brookings Institution’s Michael Greenstone and Adam Looney wrote in May. In fact, “on average, immigrant workers increase the opportunities and incomes of Americans,” they write. Foreign-born workers don’t affect the employment rate positively or negatively, according to a 2011 analysis from the conservative American Enterprise Institute. And a study released Wednesday by the liberal Center for American Progress suggests that granting legal status to undocumented workers might even create jobs.

So there you have it. Experts say it’s impossible. Can’t be happening. And if actual observed data from the real economy seem to suggest that the impossible is happening—well, Albert Einstein himself answered that one. If the material universe doesn’t support the theory: “Then I’d feel sorry for the good Lord. The theory is correct."

Before deciding whom to trust on this issue, the economists or your lying eyes, it helps to understand how the economists reached their conclusion.

Since the time of Adam Smith, economists have agreed that the secret of economic growth is specialization. Rather than everyone baking his or her own bread and sewing his or her own clothes, everyone chooses one occupation and then trades for the products others make. The more individuals specialize, the more productive everyone becomes. The more people trade, the more widely the benefits of productivity are shared.

Immigration economists apply this insight to the domestic labor market. One of the most eminent specialists in the field of immigration economics, Giovanni Peri of the University of California at Davis, offers this homely analogy:

An extreme example of this would be if you have an engineer and you add a construction worker. With the engineer by himself you’re not going to do much. But with an engineer plus a construction worker, you can build a building. Therefore, the productivity of the engineer goes up a lot. And the wages for both workers increase.

The technical term for the situation Peri is describing is “complementarity.” The labor of the engineer and the labor of the construction worker each complement the other. Immigration economists argue that immigrant labor likewise complements native-born labor. As Peri assured readers in a 2010 paper for the San Francisco Federal Reserve, "Immigrants expand the U.S. economy’s productive capacity, stimulate investment, and promote specialization that in the long run boosts productivity. Consistent with previous research, there is no evidence that these effects take place at the expense of jobs for workers born in the United States.”