Overall, a 2016 study by the Partnership for the New American Economy found that 40 percent of all Fortune 500 companies were founded or co-founded by immigrants or the children of immigrants. Taken together they employed 19 million people and had revenues of $4.8 trillion.

Opponents of a liberal immigration policy often insist they welcome legal immigrants and only object to illegal ones. Rubbish. The immigration reform bill introduced in Congress this year by Republicans Tom Cotton and David Perdue and endorsed by Donald Trump aims to cut legal immigration by half.

Restrictionists also argue that we need to favor newcomers with “skills” and educational credentials. More rubbish. Jan Koum arrived in the U.S. from Ukraine in 1992 as a 16-year-old boy with his mother, living off food stamps. She worked as a babysitter. He later dropped out of college. In 2009 he came up with an idea for a mobile messaging app. Five years later Facebook purchased WhatsApp for $22 billion.

Should it make any difference to WhatsApp’s billion-plus users that Koum arrived in the United States legally? And if it turned out that he hadn’t, should he be required to leave the country, presumably so he can pay income tax — and create jobs — in his native Ukraine?

That would be self-defeating. But it’s the fate that may soon await 800,000 or so young people who were brought without visas to the United States as children, grew up in the country, in some cases only speak English, and now face deportation because the Trump administration seems poised to terminate the Deferred Action for Childhood Arrivals, a program that allowed them to stay in school or their jobs.

The nativist wing of the right thinks DACA is unconstitutional. That’s not clear, though it would be on firmer legal ground if Congress turned DACA into law by passing Senators Lindsey Graham and Dick Durbin’s Dream Act. In the meantime, allowing these young dreamers to stay is ordinary humanity and enlightened policy. If just 10 of those 800,000 turn into future Jan Koums, the program will have more than paid for itself.