Check out Adam Davidson’s explanation of the so-called Lump of Labor Fallacy in his essay “Debunking the Myth of the Job-Stealing Immigrant.” Here is an excerpt from Mr Davidson’s excellent essay (edited by us for brevity):

“The Lump of Labor Fallacy [is] the erroneous notion that there is only so much work to be done and that no one can get a job without taking one from someone else. It’s an understandable assumption. * * * It might seem intuitive that when there is an increase in the supply of workers, the ones who were here already will make less money or lose their jobs. Immigrants don’t just increase the supply of labor, though; they simultaneously increase demand for it, using the wages they earn to rent apartments, eat food, get haircuts, buy cellphones. That means there are more jobs building apartments, selling food, giving haircuts and dispatching the trucks that move those phones. Immigrants increase the size of the overall population, which means they increase the size of the economy. Logically, if immigrants were ‘stealing’ jobs, so would every young person leaving school and entering the job market; countries should become poorer as they get larger. In reality, of course, the opposite happens. * * * immigrants tend to complement — rather than compete against — the existing work force. Take a construction site: Typically, … immigrants with limited education perform many support tasks (moving heavy things, pouring cement, sweeping, painting), while citizens with more education focus on skilled work like carpentry, plumbing and electrical installation, as well as customer relations. The skilled native is able to focus on the most valuable tasks, while the immigrants help bring the price down for the overall project (it costs a lot to pay a highly trained carpenter to sweep up a work site) … there are more native-born skilled craftspeople working today, not fewer, because of all those undocumented construction workers.”

Tear down those [anti-immigration] walls!