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The 80/20 sex myth

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The myth explained


An imaginary world where 20% of men have sex with 80% of women. In this graph, the further away the blue line representing men is away from the red line representing women, the more polygyny (men having multiple female sex partners, where the women are excusive with the man) there is. The dark grey line highlights the percentage of male and female partners the “top” 20% have.

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There’s a famous scene in the Netflix series Adolescence where one of the characters tells the other character there is a myth online where 20% of the men sleep with 80% of the women. This hateful and misogynistic myth is one which gained ground in the 2010s among far right online communities, including the “incel” community.

Whether this myth originates from a comment by one Baumeister or from a 2008 OkCupid blog entry, it has become viral on social media, even though there is no scientific evidence to support this myth.1

That in mind, I have done some research myself to see whether this myth is true.

Let’s us imagine a world where 20% of the men have sex with 80% of the women. In this imaginary world, which I have modeled, we can see that women have a fairly linear distribution of sex partners; e.g. 26.75% of women have 40.7% of lifetime male sex partners and 99.80% of women have 100.0% of lifetime male sex partners.

Contrast this with the men in this incel fantasy, where 20.95% of men have 81.7% of lifetime female sex partners, and there is a nearly 50% male virginity rate.

The actual data


The actual NSFG 2022 data. This is a “banana curve”; since the curves representing women and men both bow downwards, this shows a relative minority of people are promiscuous. Since the lines are close to each other, there is not much polygyny, but instead promiscuous men by and large have sex with promiscuous women. The black line highlights the percentage of male and female partners the “top” 20% have.

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For me to find the actual figures of reported sex partners, I looked up the 2022 NSFG data, where they asked about 10,000 men and women how many lifetime sex partners they have had.

I got the number of female lifetime sex partners from page 448 of the NSFG 2022 female codebook and male lifetime sex partners page 254 of the NSFG 2022 male codebook.2

I then took that data and made a graph of the data. Note in particular that:

Notably, both the men and women have what look to be a polynomial distribution of partners, instead of the reasonably linear distribution of partners among women we see when we model the imaginary 80/20 world incels have made up.

Also, the male and female partner count distributions are very similar to each other. This indicates that while about 20% of men have 70% of the lifetime female sex partners, about 20% of women also have about 70% of the lifetime male sex partners. So, while a small number of men do, in fact, have the majority of female sex partners, the women they are sleeping with, in turn, have a large number of male sex partners.

Methodology

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The files used to process this data and generate these graphs are available here:

https:/​/​github.com/​samboy/​blog/​tree/​main/​80-20-myth

I will explain some of the methodology below.

The simulated incel fantasy

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While it’s possible to choose, when a sexual encounter happens, to have the woman randomly choose one of the “alpha” guys 80% of the time and one of the “beta” guys 20% of the time, the code actually uses a curve.

Let’s look at the math to make such a curve:

In order to make the integration as simple as possible, let’s have f(x) be a polynomial:

Let’s integrate that equation:

Then simplify:

For n = 6, is about 0.7902848 and is about 0.8388608; those values are close enough to 80/20 and keep the math relatively simple.3

That in mind, we do the following when choosing which man will have a sexual encounter with a new partner:

The simulation has 61,000 sexual encounters with a new parter, which is approximately 10,000 multiplied by the mean number of partners women in the 2022 NSFG data have.

As an aside, this is how we could calculate the precise value to give n for a given distribution of imaginary “alpha” men in the xn function (Note: n has a value of 6 in the actual simulation we ran):

When k has a value of 80% (0.8), this simulates 80/20 (80% of the women sleep with 20% of the men), and the above equation gives a precise solution for n in this equation:

By dividing those two logarithms and subtracting one, we create an exponential degree n such that the curve y = xn has the property that the area below the curve between 0 to 0.8 is one fourth of the area below the curve from 0.8 to 1. k, having a value of 80% (0.8), represents an imaginary world where 80% of the women sleep with 20% of the men.

If we want to create an curve representing a fantasy world where 90% of the women sleep with 10% of the men, k would have a value of 0.9 (90%) with that equation and that curve function. In the resulting curve, the area below the curve from 0 to 0.9 is one nineth of the area below the curve from 0.9 to 1. One nineth because 90 in 90/10 is nine times the value of 10.

To calculate this in Lua, here k is a number between 0 and 1: 

function chad(k)
  return math.log(1-k) /
         math.log(k) - 1
end
For 80/20, the value of n is about 6.212567; for 90/10, the value is about 20.8543; and for 95/5, the value is about 57.404.

Addressing incel comments

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I will address some of the comments incels who refuse to believe this have made:

What about the 18-29 year olds?


NSFG 2022 data including data for just youth aged 18-29. The dark grey line highlights the percentage of male and female partners the “top” 20% have.

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I have run the stats on just 18-29 year olds and the numbers are not that different than they are for all ages.

If anything, the trend of there being more virgins of both genders as well as the most promiscuous people being even more promiscuous continues: While the “top” 20% of men have more partners compared to all ages, the “top” 20% of women also have more partners.

In more detail:

Note that:

Some final thoughts

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There is a slight skew, where about 5% of men (if even that) are polygynic, and about 5% more men than women are virgins, but it’s nowhere near 80/20.

Footnotes

1: The notion that women want to cheat on their male partners when they ovulate has been shown to be false.

2: Note that these are opposite sex intercourse partners.

3: 6.213 is closer to an ideal value for n to get an 80/20 curve, but 6 is good enough for this simulation.