One in five Americans older than 55 say they engaged in extramarital sex in 2016, a rate higher than their younger counterparts, University of Utah research found.

Nicholas Wolfinger, a U. Department of Family and Consumer Studies professor, published an analysis Wednesday of nearly 30 years of data from the General Social Survey, a questionnaire conducted since 1972 that catalogs Americans' attitudes and practices.

Wolfinger found that while about 16 percent of Americans reported having sex outside marriage in the past 30 years, the number of older Americans who reported doing so has increased in a trend that began in 2000, according to the study.

The number reporting extramarital sex was 20 percent for individuals older than 55 by 2016, compared to 14 percent for people younger than 55, according to the study, which does not mention how this trend may be playing out in Utah.

Because the highest rates of extramarital affairs were among those born between 1940 and 1959, Wolfinger surmises that part of the difference may be attributed to the so-called sexual revolution.

"They may have firsthand experience with 1970s-era experiments with nonmonogamy," he writes. "A few people born in the late 1950s may have had swingers for parents, leading offspring to question taboos surrounding infidelity."

Wolfinger also notes that people in their 50s and 60s have had more sexual partners in their lifetime — partly for having lived through the 1960s-70s liberalization of sexual attitudes — than their younger counterparts.

The survey asked respondents if they have "ever had sex with someone other than your husband or wife while you were married?" The question has been put to respondents since 1991.

Because the survey does not explicitly ask about adultery, Wolfinger said the data could reflect an increase in polyamory, or the practice of being involved with more than one person at a time.

But no matter how much polyamory plays a role, Wolfinger said, "old-fashioned adultery seems to have risen among older Americans."

"Even as overall divorce rates have fallen in recent decades, there has been a startling surge in 'gray divorce' among the middle-aged," he said. "Part of that story seems to be a corresponding increase in midlife adultery, which seems to be both the cause and the consequence of a failing marriage. The declining rates of extramarital sex among younger Americans seemingly portends a future of monogamous marriage. But the seeds sown by the sexual revolution continue to bear unanticipated fruit among older Americans."

astuckey@sltrib.com

Twitter @alexdstuckey