Part 5: Nobody, including the Trump administration, can prove whether immigration overall helps or hurts American workers.

My guess is that it generally helps, sometimes spectacularly so, while in other cases it hurts. A summary figure is impossible because of the complexity and adaptability of the American workplace and workforce.

What most of us may probably want, when we think about it, is for foreign workers to complement U.S.-born workers and, by doing so, create jobs for all workers. For example, bringing in a noted chef from Istanbul might enable you to launch a successful Turkish restaurant, or an Indian medical doctor might allow a community health center to stay open on weekends.

Trump’s mass deportation campaign is essentially challenging home builders to pay higher wages to attract U.S.-born workers—and to do so virtually overnight. Sometimes technology can replace foreign workers. But while using robots to replace roofers is conceptually feasible, it cannot happen until robots can carry heavier payloads.

The scenario we want to avoid is one in which employers develop a business model that depends on exploiting workers, especially those who are unauthorized, lack formal skills, or have little English proficiency.