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. In just the last few weeks, the economics department at Harvard, where I am chairman, has brought in six candidates to be considered for two assistant professor positions. Of the six, three are Americans, one is German, one is Argentine, and one is a New Zealander. The jobs will be offered to those deemed to have most promise as teachers and scholars, regardless of nationality.

The competition from foreign-born economists makes it harder for American economists to get the best positions. But it would be hypocritical for American economists to argue against such competition, as we have long preached that nations are better off over all when they pursue a policy of free and open trade. This principle applies not only to manufactured goods like textiles and aircraft but also to labor services, including lectures on economics.

The system of higher education in the United States is the world’s best in large part because it has long taken a global approach to hiring. The best students from abroad often come to the United States to earn their Ph.D.’s, and the best of these often stay here and join the faculties of American institutions. In my own department at Harvard, we have professors who were born in Canada, England, France, Italy, Spain, Austria, Poland, India and South Africa.