Colorado’s population rose by 24,059 people last year, the weakest increase measured since 1990, according to an update Tuesday from the U.S. Census Bureau. The gain, however, was enough to push the state’s population above 6 million for the first time.

Thirty-five years ago, Colorado was among a handful of oil and gas states experiencing a severe recession because of low energy prices, and from 1986 to 1990, more people left the state to pursue better opportunities elsewhere than moved in.

The state economy is chugging along this time around — not great, but not horrible. Yet, it appears high housing costs and slower job growth may be exerting a strong outward push. Last year, the state saw a weakening in its strongest contributor to population growth since the pandemic — immigration.

Nationally, President Donald Trump’s push to curb immigration a year ago lowered the country’s population growth rate from 1% in 2024 to 0.5% in 2025. Colorado’s decrease was even larger, going from a 1.29% growth rate to a 0.4%, a two-thirds decline.

Trump’s immigration crackdown led to drop in US growth rate last year as population hit 342 million

The U.S. Census Bureau measures changes in population from July 1 to June 30 every year in what is called a “vintage.” The strictest immigration policies were in place for only half that period, but they were enough to help push net immigration from 2.8 million people in the prior period to 1.3 million.

If that trend continues, the annual gain from net immigration in the next count, mid-2026, could drop to only 321,000 people, the U.S. Census Bureau estimates.

Colorado’s gain included 20,608 from natural increases, or births minus deaths. Net migration contributed 3,256 residents, with net immigration of 15,356 offsetting a net decline of 12,100 from domestic migration.

The country had an estimated population of nearly 342 million compared to 340 million in the 2024 count. The state’s population rose from 5,988,502 to 6,012,561. Colorado remains the 20th most populous state, behind Maryland and ahead of Wisconsin.

The downward shift was more pronounced in other states. California went from a gain of 232,000 residents in 2024 to a loss of 9,500 people in 2025, due primarily to reduced immigration. Hawaii, New Mexico, Vermont and West Virginia also lost population.

New York added only 1,008 people after a drop in immigration from 207,000 to 95,600. Florida saw its domestic migration drop by nearly two-thirds and immigration dropped by more than half, but it still had one of the largest overall gains, along with Texas and North Carolina.

South Carolina, Idaho and North Carolina had the highest year-over-year population growth rates, ranging from 1.3% to 1.5%.

“Many of these states are going to show even smaller growth when we get to next year,” Brookings demographer William Frey predicted Tuesday.

In 1990, the state added 18,840 residents. But the population is now 80% larger, so the comparison isn’t an even one. Although the pandemic slowed growth, the last time the rate of population growth was so low was in 1989. Only half done, this decade is shaping up to be the slowest the state has seen for growth since the 1980s.

Since 2020, Colorado has seen a net 17,729 people arrive from other U.S. states. By contrast, net immigration, people arriving from other countries, surged by 130,218. Net migration, which historically is 80% domestic and 20% international, has flipped the other way and then some.

Little on the horizon suggests that slower population growth will reverse itself, especially with fewer immigrants and now more outflows than inflows domestically. Demographic winter, long predicted, could be arriving earlier than expected.

On the plus side demographically, births rose 4.6% to 65,380 from the 2023-2024 period, and are now at the highest pace since 2017. Deaths remained fairly flat, rising by 59 or 0.1% from the prior period. That said, the holiday that death can take is limited, given the state’s aging population.

The State Demography Office had forecast a population gain of 33,154 and net migration of 13,568 for 2025. It was off by nearly 10,000, due almost entirely to weaker net migration. Last year, it had cut population forecasts through 2029 by 120,000 residents, and it may need to make more revisions, especially if immigration dries up even more.

What caused domestic migration to turn negative, given the absence of a recession? When someone arrives in a state from another country, they are counted as an international migrant. But if they move to another state, they are counted as a domestic migrant, according to the State Demography Office.

A lot of the international arrivals to Colorado between 2022 and 2025 came on humanitarian grounds and were likely headed elsewhere. And the Census Bureau, which makes no distinction between legal and illegal immigration, has gotten better at counting those arriving as refugees or under a protected status than in the past.

“At least some portion of the domestic out-migration from Colorado is made up of recently arrived international migrants,” the State Demography Office said in a release discussing the Census numbers.

That means a drop in immigration could translate into better numbers on domestic migration in the next estimate.

But an annual survey from United Van Lines, whose customers tend to be older and higher-income households, reported that Colorado last year had become a “strong outbound” state, one of only five, for the first time since 1990. For much of the 2010s, Colorado was a “strong inbound” state, before becoming more balanced after the pandemic.

That would suggest that it isn’t only the newest residents who departed, but also more established and wealthier households who were picking up and leaving.