Thread by @ImplausibleGrrl

Let's talk about a statistical artifact known as the Petrie Multiplier and how it amplifies oppression in approximate inverse proportion to the fractional ratio between a majority and a minority population. \1

en.wikipedia.org/wiki/Petrie_mu…

The original formulation was made by Karen Petrie and expressed the issue in terms of how inappropriate comments made by men to women and vice-versa have vastly unequal impacts when the group is not evenly split even if the people making the comments say them as the same rates \2

For example, let's say you have a group of 100 people. 10 of them are women, 90 are men and one in ten people in each group makes an inappropriate comment.

That is 9 inappropriate comments made by men, and 1 from a woman. \3

That means the average man in the group has a 1.1% chance of receiving one inappropriate comment while each woman has a 90% chance of receiving *at least one* such comment and a 8% chance of receiving inappropriate comments. \4

(that last part was supposed to read 'an 8% chance of receiving TWO inappropriate comments'). So the average woman in the group is eight times more likely to received TWO inappropriate comments than the men are likely to receive even *ONE*. \5

Startlingly, this idea was only formalized in the last decade.

And it applies not just to men and women and inappropriate conversational statements but to ALL forms of oppressive interactions between minority and majority groups. \6

In particular it applies to things like the commission of violence by one group against another - and the amplification factor can reach levels that can be hard to comprehend. \7

In particular, talking about transgender people, they represent only around 0.6% of the population. So in a city of say 50000 people, you will have something like ~300 trans people and ~49700 cis people. \8

Now let say that one person in 100 in each group is likely to commit an act of violence against a member of the other group in a year. That would be 3 acts of violence by the transgender people and 497 acts of violence by cisgender people. \9

That gives the average cis person a 1 in 16556 chance of being assaulted by a trans person and the trans people an *average* of 1.65 assaults on each trans person committed by cis people. \10

Sounds absurd? It isn't. Actual surveys show incredible levels of violence against trans people.

In 2013, *SEVENTY-FIVE PERCENT* of trans people in the UK reported having a hate crime committed them in the previous 12 months. \11

pinknews.co.uk/2013/08/09/stu…

This amplification of hate and discrimination by a larger group against a smaller one is a universal scaling law. It demonstrates in a hard mathematical fashion why minority groups (all minority groups) are so extremely vulnerable to abuse by a majority. \12

And it demonstrates why trying to make rules based on "equal intent" instead of "equal impact" are incredibly toxic to minorities.

Majorities, *because they are majorities*, have negative impacts on them *diluted* while minorities have it *amplified*.

\fin

Addendum: @segv_accerr pointed out that I had made some minor errors in my math. So I took the time to work up a small program to generate full (and correct) numbers which you can see here:

https://twitter.com/ImplausibleGrrl/status/1142848140829179904