President Trump usually expresses his views on immigration in terms of national security and law enforcement. But in recent days he has made a different argument for keeping immigrants out: America has no more room.

“Our country is full,” the president said on Friday during a roundtable meeting with border agents in California. “Can’t take you anymore, I’m sorry. Turn around. That’s the way it is.”

He repeated the sentiment on Saturday in a speech to the Republican Jewish Coalition in Las Vegas. “You can’t come in, our country is full,” he declared, referring to asylum-seekers. “We can’t handle any more.” In a tweet Sunday night, he made the claim yet again, demanding that Mexico block migrants heading toward the border. “Our Country is FULL!”

To be fair, Trump isn’t saying anything that others haven’t said before. The belief that America already contains as many people as it can handle is one that immigration restrictionists, both nativists and environmentalists have been promoting for years.

“The world does not need more people, and the U.S. in my judgment does not need more people either,” the prominent Princeton sociologist Charles Westoff lamented when the population of the United States passed 300 million in 2006. “It certainly does not need 100 million more.” His angst was echoed by demographer Carl Haub of the Population Reference Bureau, who plaintively asked: “Where do you go to be alone when there are 300 million people?”

Actually, you can go almost anywhere.

The United States is not remotely close to being full. Far from running out of room for more people, most of this immense country is wide-open and empty. According to the Census Bureau, nearly two-thirds of the US population live in cities — but those cities take up just 3.5 percent of the nation’s land area. Add in all the other places where Americans live — villages, islands, farms — and it still amounts to a mere sliver of US territory. In 2006, a detailed federal government study of land use in the United States reported that “urban land plus rural residential areas together comprise 154 million acres, or almost 7 percent of total US land area.” Our country, in other words, isn’t 100 percent full, it is 93 percent empty.

Of course some places in America do have a lot of people, as anyone stuck in a traffic jam, commuting in a packed subway car, or flying home for Thanksgiving can attest. But as Jonathan Abbamonte of the Population Research Institute observes, the nation’s most population-dense areas actually help demonstrate just how much elbow room Americans really have.

The nation’s most populous city, of course, is Trump’s hometown of New York, with 8.5 million residents and a population density of 28,000 people per square mile. Life in the Big Apple may not be for everyone, but countless Americans wouldn’t dream of living anywhere else. Suppose, says Abbamonte, that all Americans lived at the same population density that New Yorkers do. He did the math: At 28,000 people per square mile, the nation’s entire population would “fit comfortably in the combined area of Delaware and Maryland.” At the even greater population density of Manhattan alone — 72,000 people per square mile — “the entire population of the United States, Puerto Rico, and other US territories could reside in the tiny State of Connecticut.”

Considering that the president made a fortune building luxury housing in Manhattan, he obviously doesn’t believe that New York is full. He knows that the most crowded city in America hasn’t run out of room. Surely it should be self-evident that the nation hasn’t either.

Overall, the United States is one of the planet’s least densely-inhabited countries — it ranks 175th out of 230, far below most advanced democracies. Even without the vastness of Alaska, the United States is more thinly populated than most of the world. The European Union, for example, has roughly 300 people per square mile, nearly three times the density of the continental US.

Too many people? In many parts of this country, the problem is exactly the opposite. Population growth in the United States is at its lowest level since the 1930s, the Economic Innovation Group points out in a study released this month. In 80 percent of the nation’s counties, the population of working-age adults shrank between 2007 and 2017. America isn’t overloaded with too many people; if anything, it needs a lot more of them.

“Our biggest threat is our declining labor force,” says Governor Phil Scott of Vermont. “It’s the root of every problem we face.”

The overpopulation bugaboo is a superstition. More Americans will mean more growth, more wealth, more power, more innovation, more influence. The way to make America great again is not to turn newcomers away, but to welcome them with open arms and no resentment. For if there’s one thing America has, it is plenty of room.

(Jeff Jacoby is a columnist for The Boston Globe).