Why Do Men Lie About the Number of Sexual Partners They've Had? Scientists Have a New Answer

How many people have you had sex with? Your answer probably depends on your gender, according to a study.

In the past, sex surveys have shown men have more different opposite-gender partners than women, even though this figure should be almost even in small populations. So researchers from the University of Glasgow, U.K., wanted to find out what caused what they described as the "gender gap."

They found men are more likely to report extreme numbers of sexual partners in surveys, and to estimate a figure across their lifetime rather than keep an accurate tally.

Dr. Kirstin Mitchell, lead author of the study and senior research fellow at the University of Glasgow Institute of Health and Wellbeing, argued in a statement that reporting sexual partners accurately is vital because it helps researchers collect correct data on the spread of sexually transmitted infections (STIs), including HIV. This is a problem that has long "vexed" researchers, the authors wrote.

Researchers based in the U.K. investigated why surveys on opposite-gender sexual partners show men have more than women. Getty Images

"Most existing studies of reporting bias are limited to students or high-risk populations, or are conducted as 'laboratory' settings, so they don't show how members of the public respond in a 'real-life' survey," she said.

"To our knowledge, our study is the first attempt to look at all the key types of explanation for the gender discrepancy within the same large and representative sample."

To investigate the gender gap, the team behind the study published in the Journal of Sex Research assessed over 15,000 responses to the National Survey of Sexual Attitudes and Lifestyles (Natsal-3). Men and women aged between 16 to 74 took part in the survey.

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Men who participated in the study said they had 14 lifetime partners on average, while women said they had seven.

The researchers believe the average could be skewed by participants who overstated their sexual history. And men were more likely to do this than women.

Men who landed in the top 99th percentile of the data said they had 110 partners, while women had 50. But removing these men and women from the study lowered the overall average, and in turn closed the gender gap.

The gap got even smaller when the way individuals calculated their sexual partners was taken into consideration. That's because men were more likely than women to overestimate their partners, the authors said.

Attitudes towards sex also appeared to blur the truth, as women were often more conservative compared to men, according to the researchers. For instance, 8 percent of women regarded one night stands as "not wrong at all," compared with 18 percent of men. Women were also more likely to regard extramarital sex "always wrong," at 65 percent versus 57 percent among men. Adjusting the data to accommodate these attitudes also shrank the gender gap.

When the numbers were crunched according to sexual partners who were non-U.K. residents, this made a small difference over a five-year period and could also explain the disparity.

Another line of enquiry was paid-for sex: but the researchers found that excluding such partners made little difference to the results.

"These results are relevant to anyone who has had a partner of the opposite sex," Mitchell told Newsweek. "Participants were included in our analysis regardless of sexual orientation or identity, because individuals identifying as gay or lesbian may also report at least one opposite-sex partner."

"As long as men and women with no opposite-sex partners are also included in the analysis, the total number of lifetime partners should be equal regardless of how people identify."

Moving forward, she hopes the research will improve survey methodology "in the way we word questions; in the strategies we use to reassure participants of confidentiality; and in ensuring that survey participants do not feel in any way judged."

Dr. Cynthia Graham, professor of sexual and reproductive health at the University of Southampton, U.K, and editor in chief of the Journal of Sex Research, told Newsweek the gender gap has long puzzled researchers.

Commenting on why the research is important, she said: "This paper is the first to test several different possible explanations for this gap, using data from a large, representative sample of British men and women aged 16 to 74." The study could help researchers when assessing the number of sexual partners study participants claim they have.

However, she said some groups may have been underrepresented in the sample and it would be important for the findings to be replicated in other countries.

"In future surveys, participants could be encouraged to use a counting strategy (rather than estimating) when asked to report their number of partners," she said.

Graham concluded: "When men report having more lifetime sexual partners than women, this is most likely due to aspects of the survey methodology and misreporting due to social norms, rather than actual gender differences in the number of sexual partners that men and women have had."

This piece has been updated with comment from Dr. Kirstin Mitchell.