A surge of immigrants boosted the labor market and helped cool inflation during Joe Biden’s administration. Under Donald Trump, the flow of new workers could become a trickle.

A striking percentage of the job growth under Biden consisted of immigrant workers, economists say — with one major bank recently estimating they accounted for as much as two-thirds of the net gains over the last year. If Trump delivers on his pledge to shut down the border and conduct mass deportations, a critical supply of workers would be shut off.

The Labor Department reported Friday that U.S. employers added 143,000 jobs in January, with the jobless rate slipping to 4 percent. The growth in payrolls was lifted by new arrivals whose legal status runs the gamut. The labor force participation rate among foreign-born individuals was 66 percent in January, compared with 61.4 percent among native-born workers, according to the release.

“What happens to net immigration over 2025 is a game changer for what we should expect to see in the payroll employment numbers,” said Wendy Edelberg, a former top economist at the Congressional Budget Office who’s now the director of The Hamilton Project and a Brookings Institution senior fellow. “We should get used to much, much smaller numbers than what we’ve seen over the last couple of years.”

The White House blamed the Biden administration for soft January numbers.

“Today’s jobs report reveals the Biden economy was far worse than anyone thought, and underscores the necessity of President Trump’s pro-growth policies,” White House press secretary Karoline Leavitt said in a statement.

Trump says his sweeping agenda of deregulation, increased oil production and lower taxes will unlock growth and beat back inflation — an argument strongly endorsed by the American people in the election. But a broad-based crackdown on immigrants could slow the economy’s expansion and choke off a supply of workers that Kansas City Fed researchers and others say have alleviated staffing shortages and eased wage pressures.

Steve Englander, head of global G10 FX research and North American macro strategy at Standard Chartered Bank, says immigrant workers on temporary permits — including those who are on parole or seeking asylum — may have accounted for as much as two-thirds of the expansion in non-farm payrolls over the last year.

“It’s not clear if it’s going to be immediate — or in the next six to nine months — but by the end of the year it should be noticeable,” he said of the impact of Trump’s border crackdown.

Should those reductions occur, it could also pose challenges for Federal Reserve policymakers who use the jobs data to make decisions on inflation and interest rates.

The rise in migration during the Biden years led to substantial upward revisions to UCensus Bureau estimates, which will affect how the Labor Department accounts for population growth over the next year. Those estimates assume that net migration will continue to rise over the next year, which would buoy overall employment numbers. But Trump’s policies could push down migration, which would mean that total employment may be weaker than what’s reflected in upcoming reports.

Why does that matter? If there’s less certainty about total employment because of lower net migration, it makes it harder to understand what non-farm payrolls say about the labor market’s overall health.

“It reduces the importance that I’m putting on payroll job growth numbers — [and the] aggregate numbers — because there’s a bunch of things that we can’t observe,” Chicago Fed President Austan Goolsbee said. If “we don’t know [if] this was a month where immigration went down, if this was a month where immigration went up? It just makes me that much more skeptical of using payroll job growth as the measure.”

Of course, it’s impossible to say with any certainty the effect Trump’s immigration plans will have on future payrolls until his approach becomes clearer. Deportations could span from a few hundred thousand per year — which would be in line with those of recent administrations — or climb even higher if Congress ramps up funding for enforcement.

The president has already ordered policies that could lead to the deportation of immigrants from Cuba, Nicaragua, Venezuela and Haiti who had entered the country legally. The revocation of their legal status will limit their ability to get work permits. Still, despite a series of high-profile raids on immigrant communities in recent weeks, many of those have already been released.

And beyond deportations – including self-deportations — another confounding factor is how much of a chilling effect Trump’s policies will have on the inflow of new immigrants, legal or otherwise. Edelberg’s team at The Hamilton Project believes that net migration in the U.S. could fall anywhere between 1.1 million and negative 650,000 over the next year, depending on the severity of Trump’s policies.

“We’re all going to be guessing at what the immigration numbers really are in coming months,” she said, adding that some immigrants who arrived over the last year are still entering the labor force, which could provide a “delayed boost” in future reports.

It may take time for the market to readjust to how immigration-related shifts affect the labor market, said Sarah House, a managing director and senior economist at Wells Fargo.

“It depends on how quickly that deceleration happens,” she said. “In a year or two’s time, you could have a reinterpretation of what constitutes a good jobs number if you are seeing much slower growth in labor supply.”

Katy O’Donnell contributed to this report.