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Boulder County population dips in most recent census estimates

People leaving the county main reason for decrease
Screenshot (35)
Green counties in this map have seen population growth from 2020 to 2021, while purple counties have seen a decrease.

For the first time in at least 10 years, Boulder County saw its population decrease slightly from April 2020 to July 2021.

According to the U.S. Census Bureau, which released 2021 population estimates at the end of March, Boulder County’s population decreased 0.4% from April 1, 2020 to July 1, 2021. That’s equal to a decrease of just over 1,000 people.

It’s the first time since at least 2011 that the county saw its annual population shrink rather than grow, according to Census Bureau estimates.

The Census Bureau reported that 73% of U.S. counties experienced a natural decrease from April 1, 2020 to July 1, 2021. Natural decrease occurs when there are more deaths than births over a certain time period.

The Census Bureau pointed to fewer births, an aging population and increased mortality intensified by the COVID-19 pandemic as reasons for the rise in natural decrease rather than increase. Only 45.5% of U.S. counties in 2019 and 55.5% in 2020 saw natural decreases, the report said.

With 96 more births than deaths from April 2020 to July 2021, that was not the case in Boulder County. The decrease in population came from migration instead with a net total of about 1,400 people leaving the county from April 2020 to July 2021.

Denver, which is both a city and a county, saw the greatest population decrease in percentage over the same period in the Colorado metro area, according to the Denver Post, down 0.6% or about 4,000 people. This too was driven by net migration rather than natural decrease.

“The patterns we’ve observed in domestic migration shifted in 2021,” said Christine Hartley, assistant division chief for estimates and projections in the Census Bureau’s Population Division, in the report. “Even though over time we’ve seen a higher number of counties with natural decrease and net international migration continuing to decline, in the past year, the contribution of domestic migration counteracted these trends so there were actually more counties growing than losing population.”

Data compiled by the Denver Post found that the seven-county metro area including Denver, Jefferson, Boulder, Arapahoe, Broomfield, Adams and Douglas counties saw a total population increase of 683 from mid-2020 to 2021.

The small decreases in population are not likely to continue, state demographer Elizabeth Garner told the Denver Post. The uncertainty of the pandemic temporarily changing migration patterns coupled with the challenges COVID created for data in Census Bureau estimates should be kept in mind.

East in Weld County, population grew an estimated 3.4% from April 2020 to July 2021. The county saw a net natural increase of about 2,000 births and a migration increase of about 6,700 people.

Population estimates were not available for Longmont from April 1, 2020 to July 1, 2021.

The city, like much of Colorado, did see an increase of 12,615 people from 2010 to 2020. This makes up about a third of the population growth Boulder County saw over the same decade, adding 36,000 people.