Between the last two censuses, the adult population in the US grew 10%, from 234.6 million to 258.3 million. During that same period, the under 18 population dropped 1% from 74.2 million to 73.1 million. The decrease occurred as US birth rates hit a record low. At the same time, diversity among the youngest Americans increased in the last decade.

While there are fewer children overall, additional census data shows how America’s children have changed both demographically and geographically since 2010.

While the number of children fell 1% during the decade, the change was not uniform across demographic groups.

The number of non-Hispanic white children dropped 13%, from 39.7 million in 2010 to 34.6 million in 2020. The demographic remains the largest in the age group, though the 2020 census marked the first time non-Hispanic white children were less than 50% of the 18 and under population.

In the last two censuses, the number of non-Hispanic white people under 18 dropped.

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Meanwhile, the under-18 population grew in three demographics: Hispanic, non-Hispanic Asian, and non-Hispanic multiracial. The number of multiracial, non-Hispanic children increased 76% to 4.9 million in 2020.[1] The under-18 Asian population grew 23% to 3.9 million, while the number of Hispanic children grew 9% to 18.8 million.

The under 18 population dropped in 27 states.

While California has the most children of any state — 8.8 million in 2020 — it also had the largest decline in the under 18 population, dropping 583,000 since the 2010 census. California, Illinois, New York, Michigan, and Pennsylvania each counted over 100,000 fewer children in 2020 compared with 2010.

States that lost population in 2020 usually had large decreases in their child population.

Illinois, which lost 0.1% of its population in the last decade, had a 10% decline in children. The two states with the biggest decreases in total population: West Virginia (down 3%) and Mississippi (down 0.2%), had a 7% and 10% decrease in people under 18. New Hampshire had the steepest decline in children at 11%, but its overall population increased by 5%

Texas topped all other states in the number of children added in the last decade, growing by 6% to 7.3 million in 2020. Its overall population grew 16% in the same period.

North Dakota had the highest percentage increase of children at 22%, while its overall population grew 16% during the decade. Its child population increased by 33,000 to 183,000 in 2020. North Dakota was also the only state to experience an increase in its under 18 population share, increasing one percentage point from 22% to 23%.

North Dakota led all states in the growth of its child population.

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The connection between changing population numbers overall and change in the under 18 population is also apparent at the local level. Among the 49 counties that had more than 1 million people in 2020, 26 had a decrease in the number of kids. In Los Angeles County, the overall population increased by 195,000 or 2%. But the county also had the largest drop in children, declining by 348,000 or 15%

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On the other end, Collin County in the Dallas suburbs had a 36% overall population growth and a 24% increase in children. In all 49 of these counties, however, overall population growth outpaced the growth of the under 18 population. The result is the overall population in the US, and in many counties, is getting older.

The Census Bureau has yet to release additional data from the 2020 count on the types of households and families with children. The upcoming data releases will provide insight on how American households and families changed in the last decade.

Census data provides insight on many different groups of Americans. Dive into these demographic profiles on Asian and Hispanic Americans to learn more.

[1]

Other includes American Indian/Alaska Native; Native Hawaiian and Pacific Islander; and "some other race."

[2]

Data from the 2020 census on the racial identities of Hispanic people is not yet available