With What’s Your Number? opening in theaters this week, longstanding questions about how many sex partners people have, how many is too many, and differences between the sexes are back on the table.
In my work as a sex researcher and educator at Indiana University and The Kinsey Institute–as well as a sex columnist—I field such questions all the time. Most recently, a 28-year-old wrote to ask me whether he should break up with his girlfriend after he read an online poll that put a woman’s average number of sex partners at four (and his girlfriend’s number was nine). Although the man himself had slept with seven women, he had embraced what we scientists call the “sexual double standard.” Among the features of this cultural ball and chain is that men get rewarded for playing the field whereas women get labeled as sluts. (How dare we explore our sexuality? Back to the kitchen, ladies!) To me, this is an intriguing aspect of What’s Your Number?—that movies like High Fidelity and Broken Flowers, in which men revisit their exes, are about soul-searching with no hint of the “how many is too many?” question. And yet a movie that highlights a woman retracing her ex-steps involves the central question of her “number.”
And although I pay some attention to numbers in my professional life (after all, my job as a research scientist has me looking for patterns in people’s sex lives), I tend to encourage my students and readers not to get too hung up on their own or others’ "numbers." A person’s sexual history is only one aspect of who they are as a person, or a potential partner—and there’s more to their number than meets the eye. Consider these five surprising facts about what your number does—and doesn’t—mean:
1. It’s not exactly a slippery slope. Sure, men and women today have had more sex partners, on average, than people did 100 years ago. But we also live much longer and our numbers aren’t getting exponentially bigger. There have always been some people who had far more sex partners than others (historically, Casanova; today, Tiger Woods). And there have always been those who have remained celibate or had only one lifelong sexual partner. In between, there’s a lot of variability. These days, some research puts women’s median number of partners at around four and men’s median partners at around seven. The important thing to know is that these numbers are medians—meaning that half of people have had fewer partners and half of people have had more partners. You’re in good company on either side of the median.
2. Men and women guesstimate sex partners differently. Women tend to report lower numbers of sex partners than men, which, even accounting for same-sex couplings, makes no mathematical sense. One possible explanation is that women tend to tone down their sex numbers and men tend to exaggerate theirs—or at least to count more people as “sex partners” than women do. Other research shows that men and women estimate sex partners differently; that is, men tend to give rough guesses and women tend to tally their partners, listing them mentally by name, arriving perhaps at a more precise (and often lower) number.
3. We don’t agree on what it means to have “sex” in the first place. There’s another reason it’s difficult to get a straight answer about someone’s number: people count different things as sex. In a now-classic study published in the Journal of the American Medical Association, my colleagues at The Kinsey Institute asked men and women what they considered to be “sex.” Though vaginal intercourse was widely considered to be “sex,” 59 percent didn’t consider oral sex to be sex and about one in five didn’t view anal sex as “sex.” If you ask someone how many sex partners they had, then, you have no idea whether they’re counting all their oral, anal, and vaginal sex partners—or just one certain type of partner.
4. Biology might have something to do with it. In one study, researchers found that inbreeding may result in female flour beetles who are more open to mating with multiple males (and you don’t see flour beetles stressing about their numbers, do you?). In another study, biologists at Indiana University demonstrated that there may be advantages for junco birds who “sleep around” (nest around?) with males other than their pair-bonded partner. Chief among these: the non-monogamous birdies wind up with more grand-birds (a sign of reproductive success). Biology doesn’t only influence birds and beetles, however; in a study of more than 1,600 female (and human) twin pairs, British researchers found a moderate genetic influence related to the number of women’s sex partners.
5. You can’t tell if a person has an STI based on their little black book. It’s true that the more sex partners you have, the greater the chance you have of acquiring a sexually transmissible infection (STI)—especially common and incurable ones like the human papillomavirus (HPV) and herpes. That said, having multiple partners doesn’t necessarily mean you will get an STI—and having only one partner doesn’t mean that you won’t. I’ve met women and men who have had only one partner and yet still wound up with herpes, chlamydia, or HIV. I’ve also met people who have had a dozen partners and never wound up with an infection, to their knowledge. If you’re sexually active—whether with one person or a handful, or roomful—you should talk to your health-care provider about STI testing.