Monogamy is dominant across the world, but multiple partners are more common in rich countries, according to the study published in the Lancet.
This was despite developing countries having higher rates of sexually transmitted infections and HIV.
London School of Hygiene and Tropical Medicine researchers gathered data from 59 countries for the study.
They said factors such as poverty and mobility had more of a role in sexually transmitted infections than promiscuity had.
But the team added that the findings showed teenagers were not having sex earlier, contrary to popular beliefs.
The study said there had been no universal tread towards earlier sexual intercourse over the past three decades.
Almost everywhere, sexual activity began for most men and women between 15 and 19 years of age, with men tending to start earlier.
In the UK the average age for men was 16.5 and for women 17.5.
Researchers said most people reported only having one sexual partner in the last year.
However, those reporting multiple partners were much higher in developed countries - up to a third of under 25s in some areas - whereas only a small percentage in Africa reported the same.
And among singletons, westerners were more sexually active as well.
Two thirds of men and women without a partner in African countries reported they had had sex recently, compared to three quarters of those in developed countries.
Surprising
The researchers said these findings were surprising, as higher rates of STIs were reported in developing countries.
But the report's author, Professor Kaye Wellings, said: "This suggests social factors such as poverty, mobility and gender equality may be a strong factor in sexual ill-health than promiscuity."
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>From 30 feet away she looked like a lot of class. From 10 feet away she looked like something made up to be seen from 30 feet away.
Raymond Chandler
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