Millennials – those generally born from the early 1980s to the early 2000s – do not take on as many sex partners as the generations that came before them. At the same time, they are more tolerant of premarital sex and same-sex relationships.

Using data from a nationwide survey throughout the United States from from 1972 to 2012, a new review from San Diego State University quantified a significant shift in sexual attitudes and behavior. Not surprisingly, the “sexual revolution” of the 1960s initiated a big change in American lives: those born in the first 30 years of the last century had an average of three sex partners throughout their lifetime but the so-called Silent Generation (those born in the late 30s and 40s) averaged five sexual partners.

A dramatic change was noted, however, with the those born from the late 40s to the early 60s, also known as Baby Boomers. They averaged twelve sex partners. That appears to have been the peak as Generation Xers (those born during the late 60s and throughout the 70s) are expected to have 10 sex partners and the Millennials will average eight.

Participants in the 40 year survey numbered almost 57,000. The numbers in the study were statistically weighted to mirror the overall U.S. population.

In the early 1970s, 29 percent declared that premarital sex is “not wrong at all” but, by 2012, that number grew to 58 percent.

Reasons for the decline in lifetime sexual partners are speculated as the visibility of HIV and other sexually transmitted diseases. Additionally, a “friends with benefits” trend has young Americans having sex with their friend but not looking for new partners.