In today’s New York Times, Greg Mankiw offers a nice explanation for why many economists favor immigration:
First, many economists, especially conservative ones, have a libertarian streak. Ever since Adam Smith taught us about the wonders of free markets and the magic of the invisible hand, we have been loath to prohibit mutually advantageous trades between consenting adults. If an American farmer wants to hire a worker to pick fruits and vegetables, the fact that the worker happens to have been born in Mexico does not seem a compelling reason to stop the transaction.
Second, many economists, especially liberal ones, have an egalitarian streak. They follow the philosopher John Rawls’s theory of justice in believing that policy should be particularly attuned to its impact on the least fortunate. When thinking about immigration, there is little doubt that the least fortunate, and the ones with the most at stake in the outcome, are the poor workers who yearn to come to the United States to make a better life for themselves and their families.
Third, economists of all stripes recognize that our own profession has benefited greatly from an influx of talent from abroad.
I’d add a fourth item to Greg’s list: Many economists, both liberal and conservative, have a cosmopolitan streak. They thus place great weight on the wellbeing of foreigners, not just native Americans. From the libertarian side, that means caring about the liberty of the Mexican worker, not just the American farmer. And from the egalitarian side, that means caring about the poor immigrant worker seeking a better life, not just the person who employs them or the resident worker competing for similar work.
Such cosmopolitanism isn’t universal, of course. For example, some economists oppose greater immigration on the egalitarian, but non-cosmopolitan, concern that it would drive down wages for existing U.S. workers. On average, though, that perspective seems less common among economists than among non-economists.