 Durex's Global Sex Survey (2005) found that 44% of adults worldwide reported having had one-night extramarital sex and 22% had an affair.According to a 2004 United States survey, 16% of married partners have had extramarital sex, nearly twice as many men as women, while an additional 30% have fantasized about extramarital sex.A 2018 US study found that 53.5% of Americans who admitted having extramarital sex did so with someone they knew well, such as a close friend.