By MIKE SCHNEIDER
Associated Press

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. Buddy Lebman, a 98-year-old in the St. Louis area, said the key to longevity is good genes and staying active. He plays bridge twice a week, leads a discussion on current events at his retirement community, and is still involved with his synagogue and a school he helped found. Up until five years ago, he went on regular bicycle rides.

"I just recently had my pacemaker checked out, and the doctor told me it's good for 4 1/2 more years," Lebman said. "So I have to live at least that amount."

People reaching age 100 benefited from a century of vaccines and antibiotic developments, improvements in surgery and better treatment of diseases, said Thomas Perls, a professor of medicine at Boston University.

"Many more people who have the genetic makeup and environmental exposures that increase one's chances of getting to 100, but who would have otherwise died of what are now readily reversible problems, are able to fulfill their survival destiny," Perls said.

The Census Bureau released two earlier data sets from the 2020 census in 2021: state population figures used to decide how many congressional seats each state gets and redistricting numbers used to draw political districts.