Older Americans are cheating more on their spouses than their younger peers, new data has revealed. People in their fifties and sixties lead the way, with a fifth of them engaging in extramarital sex.

For the last three decades, the General Social Survey (GSS) in the US has collected Americans' views regarding sex outside marriage. Over this long period, three quarters of the respondents have consistently stated that extramarital sex is always wrong.

Yet, looking at how they respond to the question "have you ever had sex with someone other than your husband or wife while you were married", researchers have begun to piece together a different story.

In a brief published by the Institute for Family Studies, based on the most recent data collected by the GSS, Nicholas H. Wolfinger, a professor in the University of Utah, explains that there once was no generation gap when it came to extramarital sex. Older adults didn't cheat more than their younger counterparts.

But things began to change in 2004. Although the overall number of people who report having sex outside of marriage has held steady at approximately 16% over the past 30 years, Americans over the age of 55 started reporting rates of extramarital sex that were up to six percentage points higher than that of younger adults.

In 2016, the data indicates that 20% of Americans in their late fifties and sixties cheated, compared with 14% of Americans under the age of 55. This age gap cannot be explained by differences in sociodemographic status, ethnicity or education.

Midlife crisis or sexual exploration?

Wolfinger raises a number of hypotheses to explain the phenomenon. One is that that people in their fifties and sixties are more likely to cheat on their spouses because they're in midlife and have been married for 20 to 30 years.

However, it's also possible that the environment in which they grew up in was very different to the one young adults grew up in, and that this had an influence. These older adults came of age at a time that fostered greater sexual exploration, and this may have an impact on how they behave in their relationship.

Analysing the data in greater depths, Wolfinger suggests that this second hypothesis may be more likely. People who are now in their fifties or sixties have had more sex partners in their lifetimes than their older or younger compatriots. After peaking around 1990, rates of teen sex decreased significantly, and young people were less exposed to the ideas of sexual freedom that had characterised their elders' youth.

There has been a startling surge in 'grey divorce' among the middle-aged.

"Collectively, this sexual biography makes it understandable that products of the sexual revolution would be most predisposed to extramarital sex," the researcher writes.

Furthermore, if people just cheated as they grew old because they got bored of their marital beds, the oldest respondents (70 years old or more) would be the most likely to report extramarital sex, but that is not the case.

The rise in the number of older adults who cheat is not without consequences. Extramarital sex at midlife has been tied to a rise in the number of divorces in this age group. "Even as overall divorce rates have fallen in recent decades, there has been a startling surge in 'grey divorce' among the middle-aged," Wolfinger 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."

One of the limitation of the General Social Survey however is the fact it only asks about extramarital sex, not explicitly adultery. It's possible therefore that the data reflects rising participation in polyamory or "open marriage" - where extramarital relationships are conducted with the active permission of one's spouse.