On these fronts and others, Trump’s policies fail to recognize the interdependence of the brown and gray. Rather than fundamentally competing with younger America, older America needs it to succeed.

With the number of young whites shrinking, the kaleidoscopically diverse Millennials and post-Millennials—as well as the potential legal immigrants who might join them—constitute much of the nation’s future workers, consumers, and taxpayers. The country’s mostly white older population needs a growing workforce that propels more young people into the middle class to generate the payroll taxes that sustain Social Security and Medicare. Though political divides obscure the link, there is no financial security for the gray without economic opportunity for the brown.

The immigration debate captures this dynamic. At his contentious press briefing last week, White House senior policy adviser Stephen Miller sold Trump’s endorsement of legislation from Republican Senators Tom Cotton of Arkansas and David Perdue of Georgia to cut legal immigration in half and favor higher-skilled workers as a way to protect the economic interests of lower-skilled, native-born workers.

But the most thorough economic research has concluded that immigration poses a very limited threat to those Americans. As I wrote earlier this year, the National Academy of Sciences, in an exhaustive study last fall, found “little evidence” that increased immigration significantly affected employment levels for native-born workers. The academy did find indications that immigration has pressured wages for lower-skilled workers, but even those effects were “very small … when measured over a period of 10 years or more.” They were also confined largely to recent immigrants and native-born workers who didn’t finish high school, groups that constitute a small share of the overall workforce.

Choking off immigration as severely as Cotton, Perdue, and Trump are proposing would impose other costs. Fewer new workers would mean slower overall economic growth. (In a report released Thursday morning, the National Immigration Forum quotes one economic forecast that projects cutting legal immigration in half would reduce annual economic growth by about one-eighth.) Business start-ups would be pinched, too, since immigrants start new companies at rates exceeding their share of the population. And a big slowdown in immigration would threaten the nation’s retirement safety net.

The Social Security trustees estimate the number of seniors will grow from 48 million now to 86 million in 2050. Under the current immigration laws, the Pew Research Center projects the working-age population will increase through 2065 by nearly as much, about 30 million. Pew estimates that immigrants, who tend to be younger, and their descendants will provide the vast majority of that increase. But if legal immigration is halved, Pew projects virtually no growth in the workforce.