The new study, the first global analysis of sexual behavior, says people in western countries have more sexual partners but monogamy is nevertheless dominant across the world.
However multiple partners are more common in rich countries and this is despite developing countries having higher rates of sexually transmitted infections and HIV.
The team also found that teenagers were not having sex earlier, contrary to popular beliefs and there was no universal tread towards earlier sexual intercourse over the past three decades.
Almost everywhere, sexual activity apparently begins for most men and women between 15 and 19 years of age, with men tending to start earlier and most people polled reported only having one sexual partner in the last year.
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.
Among the singles, westerners were more sexually active as well.
Two thirds of men and women without a partner in African countries reported they had sex recently, compared to three quarters of those in developed countries which surprised the team as higher rates of STIs were reported in developing countries.
The researchers call for providing sexual health services to unmarried young women, supplying condoms, decriminalizing commercial sex and homosexual sex, and prosecuting the perpetrators of sexual violence.