Trump immigration policies, lower fertility to slow US population growth, CBO says

WASHINGTON — The U.S. population will grow by only 15 million people over the next 30 years — a smaller gain than previously projected — because of President Donald Trump’s immigration restrictions and an expected long-term decline in the fertility rate, the Congressional Budget Office said Wednesday.

The nonpartisan agency projected the nation’s population will rise from 349 million in 2026 to 364 million by 2056, a 2.2% smaller increase than it had forecast in 2025. Without immigration, the U.S. population would begin to shrink by 2030, when deaths would start to exceed births.

The revised projections carry long-term consequences for Social Security, Medicare, and the broader labor market, as an aging population and a sustained decline in domestic fertility make immigration an increasingly essential driver of U.S. population and workforce growth.

“Even if the limits on immigration and increased deportations end with the Trump administration in three years, it’s still a demographic shock,” said William Frey, a demographer at the centrist Brookings Institution.

Fertility and the Replacement Rate

The U.S. fertility rate was expected to be 1.58 births per woman in 2026 — well below the replacement rate of 2.1 — and is projected to drop further to 1.53 by 2036, where it will remain for the following two decades, according to the CBO.

For a generation to replace itself without immigration, the fertility rate must reach 2.1 births per woman. The U.S. has not sustained that level in decades, making immigration the primary variable in population calculations.

Frey said the reduction in immigration also constrains the number of children born during Trump’s term in office. “That reduces the number of kids who are going to be born in that four-year period,” he said.

Immigration Numbers and Projections

The CBO said the United States added 410,000 immigrants in 2025, down sharply from prior years. The office had separately reduced its immigration estimate for 2025 by 1.6 million in a September report, which also projected that Trump’s mass deportation plans would result in roughly 320,000 people removed from the country over the next 10 years.

The Current Population Survey estimated the number of adult immigrants fell by 1.8 million from January to November 2025, though those figures have come under scrutiny, with some experts suggesting they may reflect a decline in survey participation by immigrants rather than an actual drop in immigrant numbers.

The U.S. Census Bureau had reported that immigration increased by 2.8 million people in 2024 over the prior year, before federal enforcement tightened following Trump’s return to office in January 2025.

Immigration is projected to increase gradually through 2030, grow more slowly through 2036 — reflecting declining numbers of international students and temporary workers — and then accelerate to an average of 1.2 million people a year from 2037 to 2056, the CBO said.

Labor Force Pressure

Social Security and Medicare, already strained by an aging population, face growing pressure as fewer workers than expected pay into the system. The labor force participation rate stood at 62.5% in January 2026; demographers say that share will be increasingly difficult to sustain as the cohort of retirees grows relative to working-age adults.

By the end of this decade, all of the nation’s baby boomers — born between 1946 and 1964 — will be over age 65, the CBO noted.

Kenneth Johnson, a senior demographer at the University of New Hampshire, said in an email that the consequences extend beyond immediate headcounts.

“These immigrants bring both themselves and the potential for children in the near term,” Johnson said. “They contribute both to the labor force through their arrival but also to the potential future growth of the US population through their potential to have children in the near term.”

Policy Context

Trump returned to office in January 2025 and moved quickly on immigration enforcement. The administration deployed Immigration and Customs Enforcement agents in U.S. cities, imposed visa bans on applicants from certain countries, and worked to extend the U.S.-Mexico border wall.

Trump’s tax and spending law, passed by Congress and signed in July, included roughly $150 billion for deportation operations over four years, covering detention center construction, border wall extension, and additional law enforcement personnel.

The CBO projected the total U.S. population will stop growing in 2056, after which the country’s population would remain roughly flat from year to year. The agency’s report underscores a demographic reality that economists and demographers have long noted: at current fertility rates, immigration functions not as a supplement to natural population growth but as its primary engine.