The Petrie Multiplier
Updated 2026-08-08
INTRODUCTION
English translation pending.
CORE DEFINITION
Named after Karen Petrie, who described it in the context of women in computing. Suppose men and women each behave badly at the same low rate. If the field is overwhelmingly male, the small number of women receive hostile remarks from many men while each man rarely meets a woman to receive one from. The harassment experienced per person therefore scales with the ratio between the groups rather than with the moral quality of either. The multiplier is structural: it comes from the arithmetic of who is exposed to whom, not from the majority being unusually malicious.
SCAFFOLDING EFFECT
Reduce cognitive load
- Ratio check: Compute the exposure each minority member faces before declaring an environment welcoming. - Policy sizing: Add protection proportional to the imbalance rather than to the average experience reported. - Attrition forecast: Expect departures to track exposure rates rather than the number of formally reported incidents.
Anchor fast decisions
Harassment is an interaction between a sender and a target. If almost everyone belongs to group A and a handful belong to group B, then nearly all cross-group interactions have a B member as the target. Assuming equal base rates of bad behaviour, the per-person exposure for B is multiplied by the size ratio of A to B. Felt hostility is therefore a function of composition, and small changes in the minority headcount move the multiplier sharply.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Petrie_multiplierverified
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