Even before the Supreme Court ruled Thursday that President Trump has broad power to deport hundreds of thousands of migrants living legally in the U.S. under temporary protected status, David Bier feared the U.S. was slipping toward a demographic cliff.
"We're destined to be there, in short order, there's no question," Bier said. "We're already seeing a situation where most counties in the United States had more deaths than births."
An expert on population and immigration at the libertarian Cato Institute, Bier believes the U.S. is beginning to look more like China, Italy and South Korea — nations that face rapid aging and population decline are seen as a crisis.
U.S. birthrates have been declining for decades. There are far too few children born each year to maintain a stable population.
Until last year, high rates of foreign immigration largely offset that trend. But for the first time since the 1930s, during the Great Depression, the U.S. now faces record low birthrates and low numbers of migrants at the same time.
"Our higher birthrates of a century ago are not coming back. There's no way to have a sustainable fiscal and economic situation that doesn't involve immigration," Bier said.
Trump's legal fight to end temporary protected status for hundreds of thousands of Haitians, Syrians and others living in the U.S. legally is only one part of a wider administration effort to squeeze immigration.
The Supreme Court also ruled this week that the administration has authority to block most asylum seekers from entering the country. Federal agents have also conducted raids in cities across the U.S., to accelerate deportations.
Last month, Trump issued an executive order that could make it harder for many migrants living in the U.S. without full legal status to use banking and financial services.
Many immigration opponents see these changes as progress. In a statement following this week's Supreme Court decisions. A spokesman for the Federation for Immigration Reform said Trump should have full authority to direct who enters the U.S.
"Our immigration laws are written to be pro-enforcement, not anti-enforcement," said FAIR's Christopher Hajec.
But according to Cato's Bier, Trump's policies are already reshaping the demographics of communities, meaning there are fewer workers, consumers, taxpayers, and children in schools.
"If you're not allowing immigration, you're going to have [an aging and] a declining population and that creates all kinds of problems," Bier said.
Economists say that without migrants, the number of young workers paying into Social Security will fall more rapidly; schools in many areas will close; and the number of young families having children will decline.
Census data already shows big changes to U.S. population
The immigration decline under Trump is dramatic. In 2024, roughly 2.7 million foreign migrants entered the U.S., according to the Census Bureau. This year, census experts predict that number could drop as low as 300,000. Some demographers believe the U.S. may be reaching a point where more migrants are leaving than entering.
Impacts of this massive shift on America's wider population are already emerging. Studies by the Census Bureau, the Congressional Budget Office, and the Federal Reserve all point to a more rapidly aging national population under Trump.
Population growth in the U.S. fell by half in 2025 from the previous year, with five states losing population. Census data shows the total number of young Americans, those under age 25, is already falling nationwide.
William Frey, a demographer at the liberal-leaning Brookings Institution, described last week's Supreme Court rulings as "alarming." He believes without robust foreign immigration, more states will quickly see their populations stagnate or decline.
"Not just in big immigration states, but in places that have relatively small numbers of immigrants, you know, Iowa, Kansas, Nebraska — those states require immigrants to get any population growth," Frey said.
Even before Trump's policies curbed immigration, the U.S. population was expected to decline later this century. Experts say low immigration rates will cause that downward trend to happen much sooner.
According to Frey, the U.S. has time to reverse course. But he believes the Trump administration is committed to lowering both legal and illegal immigration over the long term, a policy he described as dangerous.
"This is as clear as the nose on your face," he said. "You've got to have this growth in the younger population if you're going to survive. Immigration is a key part of that going forward."
"America's doors are closed"
The Trump administration sees this very differently, describing foreign migrants not as people who sustain state populations and economies, but as a social burden and a threat.
"America's doors are closed fully to asylum seekers," Stephen Miller, one of Trump's top White House policy advisors, said on Thursday.
Speaking with reporters, Miller described the Supreme Court rulings as a victory and said ending birthright citizenship for the children of migrants born in the U.S. is the next step.
"This country doesn't have a future if we don't end birthright citizenship," Miller said. Justices are expected to rule on birthright citizenship as early as next week.
This kind of opposition to both legal and illegal immigration is now widespread among conservatives, said Cato's David Bier, who worked as a Republican congressional staffer on immigration policy.
He told NPR that when he talks to conservatives about the economic and demographic risks of closing the country's doors to migrants, many answer with a cultural argument. "[They] would rather have a declining population of 'true Americans' than have an economy kept afloat by people who don't share [their] values," Bier said.
But if extremely low or zero-level immigration does become the new normal for the U.S., experts say it would swiftly remake the fabric of the country. The Census Bureau estimates that without robust migration in the coming years, total population loss by the end of this century could exceed 107 million people.
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