Musings on the Petrie Multiplier

I was (not so) recently made aware about the existence of the Petrie multiplier. A mathematical “proof” of how the ratio between ingroups (e.g., men) and outgroups (you guessed right, women) can have an effect on how the average experience of a member of the outgroup will look like. I’m oversimplifying things here, so if you’re interested on reading in depth you can take a look here.

Now, I’m a very visual person so I decided to quickly sketch some code and show a graph of how this would look like. You can take a look at the graph down below.

% the vis here

The Rules of the game are simple:

  • We define a numbered set of people
  • We define a ratio between ingroup/outgroup (men, and women)
  • We also define a fixed number of instances of events

With these, we are able to see how experiences vary: when the ratio is very close to .50, the experience is pretty sensitive to the amount of incidents (well, obviously). However, what’s particularly interesting is how the experience becomes very sensitive to the ratio. Even with a small number of incidents, a very uneven ratio will have a drastic effect on the average outgroup experience.