Population growth in Colorado, which had helped drive the region’s burgeoning economy over recent years, has slowed markedly, with some counties in metro Denver experiencing losses, according to a new report.

From 2024 to 2025 the state added just 33,151 residents, marking one of the lowest annual growth cycles it had posted over the past decade, according to a study issued last week by the Greenwood Village-based Common Sense Institute.

That recent total shows Colorado’s annual population growth having slipped by some 60% from 2015, a summary of the study concluded. During the span of 2015 to 2016, Colorado saw a population increase of 83,036, the study said.

Meanwhile, although recent data show the state is still gaining residents, those tend to be concentrated in a small number of counties, according to the report.

Meanwhile, some other counties that had reflected growth in previous years are now posting declines, the study said.

Most prominent of the growth areas is Weld County, north and northeast of the Denver metro area, which the CSI study said added another 8,651 residents during 2024 to 2025. The county has posted a population increase of near 33 % over the past decade, as opposed to just under 10% for the state as a whole.

Boulder losses, Douglas gains

Douglas County added 7,181 residents over the recent span, showing only a slight decline in its rate of growth over the decade, the study said. Adams County saw a growth of 4,836 residents over the recent term.

However, Jefferson and Arapahoe Counties posted losses over the same timeframe. Jefferson County’s population declined by 600 residents from 2024 to 2025 — the largest population decline in the state, the study noted.

Arapahoe County saw a net out-migration of 1,884 residents. Both Jefferson and Arapahoe counties experienced overall declines in migration in excess of 125% over the decade, it said.

Migration and population totals represent different entities, the report noted. Population reflects the total residents residing in a county, while net migration reflects the number moving into the area, balanced against the number moving out during the period.

Although the state continued to post continuing arrivals of new residents, those have dropped off 80% over the decade — from 68,844 net arrivals in 2015 to 13,568 in 2025, according to the report.

“Colorado’s population is still growing, but the geography of that growth has changed,” the report said in a summary.

“Recent gains are increasingly concentrated in a smaller group of counties, while several large metro and mountain counties are growing slowly, losing population, or attracting fewer net new residents than they did a decade ago.”

Report authors Jimena Sanchez and Cole Anderson noted that the evolving patterns would have impacts on key economic indicators, including housing demand and labor availability. Trends in population and migration were obtained from analysis of State Demography Office data, using 2025 as a baseline, the study said.

In addition to Jefferson County’s loss over the recent two-year span, Boulder County saw a loss of 556 residents, and Eagle County lost 481, the report noted.

Along with increases in net migration to Weld County, Douglas County saw 5,306 arrivals and Mesa County attracted 1,683.

Counties experiencing net migration losses included Arapahoe County (-1,884), Jefferson County (-1,225) and Denver County (-903).

Report authors went on to note that no attempt was made to identify the causes if population and migration shifts, other than to say that housing affordability, job location and remote-work patterns could affect the numbers.