America aged rapidly in the last decade as baby boomers grew older and births dropped

The United States grew older, faster, last decade.

The share of residents 65 or older grew by more than a third from 2010 to 2020 and at the fastest rate of any decade in 130 years, while the share of children declined, according to new figures from the most recent census.

The declining percentage of children under age 5 was particularly noteworthy in the figures from the 2020 head count released Thursday. Combined, the trends mean the median age in the U.S. jumped from 37.2 to 38.8 over the decade.

America’s two largest age groups propelled the changes: more baby boomers turning 65 or older and millennials who became adults or pushed further into their 20s and early 30s. Also, fewer children were born between 2010 and 2020, according to numbers from the once-a-decade head count of every U.S. resident. The decline stems from women delaying having babies until later in life, in many cases to focus on education and careers, according to experts, who noted that birth rates never recovered following the Great Recession of 2007-2009.

“In the short run, the crisis of work-family balance, the lack of affordable child care, stresses associated with health care, housing, and employment stability, all put a damper on birth rates by increasing uncertainty and making it harder to decide to have and raise children,” said Philip Cohen, a sociologist at the University of Maryland.

There are important social and economic consequences to an aging population, including the ability of working-age adults to support older people through Social Security and Medicare contributions.

The Census Bureau calculates a dependency ratio, defined as the number of children plus the number of seniors per 100 working-age people. While the dependency ratio decreased for children from 2010 to 2020, it increased for seniors by 6.8 people.

At the top end of the age spectrum, the number of people over 100 increased by half, from more than 53,000 people to more than 80,000. The share of men living into old age also jumped.