In this Tedx talk about sexy mathematics, Dr Clio Cresswell says that there is an inconsistency between womens' and mens' reports of the number of sexual partners they have had.

Now, men report, on average, having had sex with two to four times as many women as women to men. And this does not make sense.

Creswell argues that this results from the difference between the way they count their partners: Men estimate; women enumerate.

She quotes one particularly interesting piece of evidence that this is true: at about 6:06 in the talk she claims that the key piece of evidence is that 80% of mens' estimates of the number of partners is divisible by 5.

Is her hypothesis (that the key explanation of the different reported numbers results from women counting and men estimating) consistent with other research?

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    It is interesting that for heterosexuals, men have more sex than women. So the question is, “who with?” Dec 24, 2016 at 17:53
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    I would think a larger factor would be that men are counting women who are not surveyed - sex workers, for example. Dec 24, 2016 at 19:06
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    @KateGregory And, again, the nature of the data bins on most such surveys. They have a top bin, the stud that slept with 200 and the prostitute that slept with 10,000 end up in the same bin. Dec 24, 2016 at 20:12
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    Men are likely to lie by overcounting and women by undercounting. That's an stereotype that could be true for people enough to affect means.
    – Pere
    Dec 26, 2016 at 23:26
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    @jamesqf It's possible that you're underestimating. I've never been rich or a celebrity, but I lost count a long time ago. One night stands just aren't/weren't significant enough to make note of. Maybe it's a generational thing. I'm in "the generation which hit sexual maturity before AIDS and herpes". Dec 28, 2016 at 14:23

1 Answer 1


There are studies that support what she is saying to some extent, but she is exaggerating.

For example in Estimating number of lifetime sexual partners: Men and women do it differently 1999 (alternative link) Just looking at the top 10% (above the 90th percentile for men and women as one dataset, meaning more than 8 partners) men and women, as plotted in Fig. 1, the men are reporting numbers like 10, 15, 20, 25, 30, 35, 40, 50, 60 and 70, while the women are doing this to a lesser extent.

However, looking at the full data set men have a mean number of 3.79 partners and women 2.54 partners.

And when the top 10% were excluded men averaged 1.51 partners and women 1.53 partners.

So, the part about 80% reporting a number divisible by 5 is inconsistent with this data, as too many report a number less than 5 for this to be true. The 80% figure is only possible if you are looking at a tail-extreme subset like Fig. 1 of the above article.


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