American Millennials may be even more sexually permissive than the 1970s generation, noted for its bisexuality and drugs and unprotected sex in a consequence-free environment.

Teen sex, premarital sex, gay sex, it's all a lot more commonly accepted than was the case 40 years ago, but Millennials haven't embraced '70s-era Swinger parties: Affairs while married are bad, according to analysis of surveys led by psychologist Jean M. Twenge of San Diego State University. 

Their conclusions were drawn from data in the nationally representative General Social Survey, conducted in most years since 1972. Overall, surveys suggest that rising cultural individualism has produced an increasing rejection of traditional social rules, including those against non-marital sex, particularly among Millennials born between 1982 and 1999. In the 1970s, 29 percent of American adults believed premarital sex "was not wrong at all," compared to 42 percent in the 1980s and 1990s, 49 percent in the 2000s, and 55 percent in the 2010s. One sexual partner was the norm for those born early in the 20th century, but those born in the 1950s through the 1990s who were surveyed said three to four partners was more common - and most of those were lying.

According to Twenge, the survey trends may be due to shifting religious beliefs, the rising age at which people marry, and norms around unmarried parenthood. With more Americans waiting until their late 20s or later to marry, they have more opportunities to engage in sex with more partners and less reason to disapprove of non-marital sex.

"As individualism increased in the US, sexual attitudes and behavior became more permissive and less rule-bound," says Twenge. "More Americans believe that sexuality need not be restricted by social conventions. Recent generations are also acting on this belief, reporting a significantly higher number of sexual partners than those born earlier in the 20th century."

Citation: Reference: Twenge, J.M., Sherman, R. A.,&Wells, B. E. (2015). Changes in American Adults' Sexual Behavior and Attitudes, 1972-2012, Archives of Sexual Behavior. DOI 10.1007/s10508-015-0540-2