Sexual Numeracy

My probability class inspired me to put that knowledge to use on a topic that's always interested me. So, here we go.

Given that our world grows by 2 million (2 * 10⁶) people every two weeks, that our world population as of last week was estimated at 6,140,822,271 people, and assuming people have unique parents (monogamous relationships) and only single-child births...

285,714 people are having sex every day.

Given that contraceptives and sexual education are not available on a worldwide basis, let us continue under the assumption that child-bearing sexual encounters are the only such occurrences.

Assuming a uniform sex distribution - that is, proportionate to population, sex is as likely to occur in Worcester as it is in London, Tokyo, or Kosovo - and given that as of 7:04 PM EST on January 13th, the U.S.A. consisted of an estimated 283,988,943 people...

13,229 Americans are having sex each day.

Assuming the WPI student body consists of 4,000 (4 * 10³) people who do not have sex with non-WPI students...

0.19 (1.9 * 10^-1) students have sex each day - or, one person has sex roughly every five days. And it takes two people to have sex! That means in a given school year in session (not counting breaks, summer, etc.), about 26 students have sex. The odds of any given student having a child-bearing sexual encounter in her four years here is 2.6%, while the odds of her having sex each of the four years is a mere 0.17%.

Let us end our formal speculation here. However, if we wish to take into account the existence of contraceptives and other techniques, as well as non-child-bearing sex, by what factor can we multiply the sexual frequency at WPI? That is, how many sexual encounters produce children? One in ten? 100?

If 100 sexual encounters occur for every child (generous?), then 18 people have sexual encounters every day. This is assuming those two people do not have sex with other people, which would increase the availability of sexual partners.

If, say, every second person does have sex with someone else - or, out of every sexual encounter between two people, one will not remain faithful (you can also add some off-campus relationships to this number) - then 28 students have heterosexual sex every day. Given one school year in session (not counting breaks, summer, etc.), 3,920 students, or 98% of the entire student body, has sex in one school year. Or, the average WPI student can expect to have sex at least once per year.

The numbers back it up, so it must be true.