Millennials may have popularized hookup culture and the notion of “friends with benefits,” but social scientists have made a surprising discovery about the sex lives of these young adults — they’re less promiscuous than their parents’ generation.

The average number of sexual partners for American adults born in the 1980s and 1990s is about the same as for baby boomers born between 1946 and 1964, according to a study published this week in the journal Archives of Sexual Behavior.

But that number is determined by a combination of factors — the time period when people reach adulthood, their age at the time they are surveyed, and the generation they’re in. When the study authors used statistical methods to separate out those three factors, they found that a person’s generation was the biggest predictor of the number of people he or she had slept with.

In their calculations that isolated these so-called generational effects, the average number of partners for a baby boomer born in the 1950s was 11.68. The comparable figure for millennials was 8.26, the researchers found.


The statistics in the study were drawn from the General Social Survey, a project based at the University of Chicago that has been collecting data on the demographics, attitudes and behavior of a nationally representative sample of American adults for decades.

The survey results revealed steady growth in the acceptance of many kinds of sexual behavior since the 1970s. For instance, back then, only 29% of Americans as a whole agreed that having sex before marriage was “not wrong at all.” By the 1980s, 42% of people shared this view. That proportion climbed to 49% in the 2000s, crossed the 50% mark in 2008, and reached 55% in the current decade.

The dwindling disapproval of premarital sex was particularly evident when the researchers compared the views of young adults in each generation. When baby boomers were between the ages of 18 and 29, 47% of them thought that sex before marriage was just fine. When Generation Xers were in the same age range, 50% said it didn’t bother them. And by the time millennials were in their late teens and 20s, 62% said premarital sex was OK.

“The changes are primarily due to generation — suggesting people develop their sexual attitudes while young, rather than everyone of all ages changing at the same time,” said study leader Jean Twenge, a psychology professor at San Diego State University. “This has caused a large generation gap in both attitudes toward premarital sex and number of sexual partners,” she explained in a statement.


It’s probably no coincidence that acceptance of premarital sex rose as people waited longer to get married, the researchers wrote. In 1970, the median age at which women married for the first time was 21, and for men it was 23. By 2010, those ages rose to 27 and 29, respectively.

“With more Americans spending more of their young adulthood unmarried, they have more opportunities to engage in sex with more partners and less reason to disapprove of nonmarital sex,” Twenge and her colleagues wrote.

Same-sex relationships are also coming into their own, according to the study. Until the early 1990s, only 11% to 16% of Americans approved of such relationships. But that trajectory changed rapidly beginning in 1993, with 22% approving of gay and lesbian relationships. By 2012, 44% of the public was accepting of same-sex couples.

Once again, millennials led the way — 56% of millennials in their late teens and 20s said they had no problem with same-sex relationships. Only 26% of Gen Xers felt the same way when they were that age, as did a mere 21% of baby boomers, the researchers found.


And millennials were the most likely to acknowledge having casual sex. Fully 45% of them said they had slept with someone other than a boyfriend/girlfriend or spouse when they were in their late teens or 20s. When Gen Xers were that age, only 35% of them said they had sex with someone who wasn’t their significant other. (The comparable figure for baby boomers wasn’t reported.)

But if millennials are more willing to have casual sex, it doesn’t necessarily mean that they’re willing to sleep with more people, the social scientists noted. “While these partnerships are casual in nature, they may be defined by regular contact between a limited number of individuals, perhaps reducing the overall number of partners,” they wrote.

Americans in general have become more open to the idea of teenagers having sex — 6% of people surveyed in 2012 said they were fine with it, up from 4% in 2006. Meanwhile, they’ve become less tolerant of extramarital sex — only 1% of people accepted it in 2012, down from 4% in 1973.

The HIV/AIDS epidemic of the 1980s and 1990s seems to have influenced Americans’ attitudes about sex, according to the researchers. Acceptance of sex outside of marriage “dipped slightly” during the years when “public attention to AIDS was at its height,” they wrote.


Twenge, who worked on the study with colleagues from Florida Atlantic University in Boca Raton and Hunter College in New York, said the increasingly permissive attitudes toward sex are a sign of the rise of individualism in America.

“When the culture places more emphasis on the needs of the self and less on social rules, more relaxed attitudes toward sexuality are the almost inevitable result,” she said.

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