An Unlikely Coincidence, Part 2: The Numbers

A few fun numbers, as a followup to the recent post about the unlikely coincidence of Leslie Bradshaw and I both graduating from the same high school in the same year.

Approximately 3.5 million kids graduated from high school in the US in the year 2000. Of those, using stats from the Bureau of Labor Statistics, approximately 21,000 are management-level.  Assuming that only 1 in 100 managers is a founder, that’s 210 founders. That means the hit rate for founders in that particular year is about 1 in about 17,000.

If we accept those postulates, the chances of Leslie and I coming from the same 150-person high school graduating class (assuming that JCHS/Oregon/other shared environments had no unique effect) is 1 in about 13,000.

For reference, that’s about half as likely as the average American (AKA you) getting shot to death (thank you, National Security Council, for that cheery thought).

2 replies
1. Mike says:

I think you need to take into account that your status as a founder is already a given in the equation, so you really should only calculate the probability that *one* other person in your graduating class is a founder, not the likelihood that two people in any particular 150-person graduating class are founders.
The answer is therefore more like 1 out 114 – you have ~150 chances to find at least one founder in your class, so really the probability that *you* will do so is 1-(likelihood that none are founders). The probability that *none* are founders is (likelihood of a particular individual *not* being a founder)^150. The probability of a particular individual not being a founder is 1-(likelihood of *being* a founder).
Plugging the numbers in, then, the probability that *at least one* other person in your class is a founder is
(1-(1-(1/17000))^150) = .0088 = 0.88%, which is roughly 1 out of 114. This is still very unlikely, but not nearly as unlikely as you getting shot to death.
Your analysis is correct for any particular 150-person graduating class having two founders, however, so it’s definitely a rare occurrence in general, but much less unlikely for you in particular!
This doesn’t at all take into account the possibility of you actually meeting, however… that significantly reduces the overall likelihood of the encounter, but is somewhat more difficult to estimate. If you had a sense of how many of the 210 founders from the class of 2000 you’ve actually met, you could get a ballpark figure.

2. matt says:

And here I thought it was going to be that I got the actual math wrong. *laughs*
I think, at least for me, the fascination is not really about me and Leslie (special snowflake status aside) but really that two founders came from the same class of 150. So I don’t take my founder status as a given – indeed, the I am actually truly interested in two founders coming from the same small class as independent events.
That said, I like the idea of thinking about how many of the 210 I’ve met…the problem is that I don’t have the faintest idea. It is remarkable how little age tends to come up in conversation and generally, when it does, it is because someone is surprised at how young someone is.