The number of female affairs still lags behind male dalliances. For every two women like actress Meg Ryan, who exchanged cheating accusations with her ex-husband Dennis Quaid, or Paula Broadwell, the biographer-turned-mistress of former CIA Director David Petraeus, there are three men like former President Bill Clinton, pro golfer Tiger Woods or onetime South Carolina governor, and now U.S. congressman, Mark Sanford, who have been the focus of much-publicized reports of extramarital affairs.
As the nation's median age increases, changes in attitudes about women engaging in sex with someone not their spouse may cause the gap to narrow more, Bergner said.
"Once you strip away the stigma from the equation, interest in casual sex is about equal for women and men," he said. "So we men may have a lot to worry about."