A record number of U.S. 40-year-olds have never married and most live alone, according to a new analysis of Census Bureau data going back more than a century.

The Pew Research Center reported Wednesday that 25% of 40-year-olds in 2021 had never been married, up from 20% in 2010. Most lived alone, with just 22% of never-married adults ages 40 to 44 reporting last year that they cohabitated with a romantic partner.

The trend is “notable because the share of 40-year-olds who had completed at least a bachelor’s degree was much higher in 2021 than in 1980,” 39% vs. 18%, said Richard Fry, a Pew senior researcher.

“More-highly educated 40-year-olds are more likely to have married, but the growth of this group has not reversed the overall trend of delaying or forgoing marriage,” Mr. Fry said in a summary of the findings.

In the 1900 Census, 16% of 40-year-olds reported never having been married, a number that gradually dropped to a low of 6% in 1980. The number has risen steeply every year since then.

According to Pew, people born starting in the 1960s have increasingly delayed marriage and a growing number have not wed.

In a separate report on May 23, Pew noted that young adults are reaching key life milestones later than earlier generations. Those aged 21 are less likely today than four decades ago to have achieved a full-time job, financial independence, independent living and parenthood.

According to the nonprofit research center, many young adults may still tie the knot later in life. On Wednesday, Mr. Fry noted that about one-in-four unmarried 40-year-olds in 2001 had wed by age 60 two decades later, in 2021.

“If that pattern holds, a similar share of today’s never-married 40-year-olds will marry in the coming decades,” Mr. Fry said.

• Sean Salai can be reached at ssalai@washingtontimes.com.