Middle-class men have fewer sexual partners on average than their richer and poorer counterparts, and even fewer if they're straight, new research has found.
Straight women have fewer sexual partners too, but so do lesbians - it's bisexuals who take home the trophy for the female gender, the University College London study found.
Researchers used data collected by the English Longitudinal Study of Ageing, which looks at the health of wellbeing of older Brits, to get a life-long look at sexual behaviours and how they differ between the sexes over their entire lifetimes - not just in their youth.
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They found for women, white bisexuals who enjoy regular "vigorous physical activity" who don't have long-running illnesses have the most sexual partners.
"Vigorous physical activity is usually achieved via participating in sport," the researchers said. "Sport participation has been shown to track across the lifespan and may provide a setting for social interaction, thus increasing the potential to meet a greater number of potential sexual partners."
White women racked up more than others, the researchers suggesting "cultural norms" are preventing Asian and Muslims from adding to their tallies.
While for men, being gay and either rich or poor were strongly correlated - and ethnicity didn't matter.
"This is of clinical importance, given that gay men are a key population with a high prevalence of HIV and a greater number of sexual partners is known to increase the risk of HIV transmission," the researchers said, adding that it's unclear why non-white men didn't have trouble adding to their tallies.
There are a few other attributes correlated with the number of sexual partners for men, and not all of them good. For whites they are using alcohol and drugs, fighting, carrying weapons and engaging in 'dating violence'; for black men, binge drinking.
For both sexes, not getting married was correlated with having a greater number of sexual partners, "unsurprisingly" as the researchers put it - but there was a catch.
"The frequency of sexual activity reported by this population compared with those who are married is lower."
Smoking and alcohol consumption correlated with more partners for both sexes, but as the study notes, has also been previously linked to increase rates of HIV.
As for the sheer number of sexual partners, men - again unsurprisingly - claim they've had a lot more than women. Forty percent of men say they've had at least five, but only a quarter of women. One in five men say they've had 10 or more, compared to less than one in 10 women.
The latest study was published in journal BMJ Sexual & Reproductive Health.