Behold the great orgasm gender gap.

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Orgasms: His vs. Hers

Speaking to The Daily Beast in 2009, Stanford University sociologist Paula England declared the uneven ratio of male to female orgasms "as serious as" the $6-per-hour gender wage gap in the U.S. [source: Seligson]. Virtually any way researchers slice it, men edge out women in terms of how often they're experiencing the Big O. During one-night stands in particular, female participants are extremely unlikely to orgasm. According to a Stanford University survey of almost 13,000 heterosexual college students, 44 percent of guys were likely to finish during those fleeting encounters, compared to 19 percent of the female co-eds [source: Young and England].

Even in steady relationships, straight men may overestimate female partners' orgasm frequency. The 2010 National Survey of Sexual Health and Behavior conducted by Indiana University found that 85 percent of men say their partners climaxed during their last sexual encounter, whereas only 65 percent of women concur. Perhaps unsurprisingly then, 64 percent of women reported being "very satisfied" with how often they achieve orgasm [source: Indiana University].

Granted, the orgasm gap closes when focusing in on different categories of sex. For starters, when discussing intercourse with dedicated sexual partners, the regularity of female orgasm surges to 79 percent [source: Pappas]. Integrating clitoral stimulation, as opposed to exclusively vaginal penetration, also greatly improves the chances of climaxing to roughly 90 percent [source: Kinsey Institute]. That may underlie why Alfred Kinsey's early surveys found that nearly 68 percent of lesbian partners report climaxing 90 to 100 percent of the time, versus 40 percent of heterosexual married women [source: Goldstein and Davis]. In addition, multiple reports have shown that women tend to rate clitoral orgasms as more satiating throughout the entire body, compared to vaginally-stimulated orgasms [source: Mah and Binik].

On average, men's orgasmic latency through vaginal intercourse, or the time it takes from start to finish, is faster than women's by a difference of between 8 and 15 minutes, on average [source: Brown University]. That said, women may well be justly rewarded for their patience with orgasms lasting between 13 to 51 seconds, while men max out at 10 to 30 seconds [source: Bolin and Whelehan]. And unlike the male refractory period following ejaculation that prevents the body from immediately chasing down another orgasm, women's pelvic floor muscle contractions can continue to deliver multiple orgasms. In 1953, Kinsey estimated that 14 percent of the American female population could muster multiple orgasms, whereas a 1991 study published in the Archives of Sexual Behavior found that 42 percent of its female sample self-reported multiorgasmic events [source: Darling, Davidson and Jennings].

At the same time, those ladies-only bonuses complicate one of the most burning -- and contentious -- questions in the evolutionary biology community: Why do women have orgasms to begin with?