The Peter Principle
In a hierarchy, people rise to their level of incompetence.
Laurence Peter, 1969. The mechanism: people get promoted based on their performance in their current role. Eventually they get promoted into a role where their performance is no longer impressive (they've hit the limit of their competence). At that level, they stop getting promoted. They stay there.
The implication: over time, organisations fill up with people performing at a mediocre level in roles slightly above their actual competence. The famous corollary: most useful work in any organisation is done by people who haven't yet reached their level of incompetence.
For operators, the principle warns against promoting purely on past performance. The skills that make a great IC don't always make a great manager. Promotion needs to assess fit with the new role, not just success in the old one.
Examples in the wild
The best salesperson getting promoted to sales manager is the classic Peter trap. The skills don't transfer. The company loses the salesperson and gains a mediocre manager.
Founders who scale a company from 10 to 100 people often hit their ceiling. The next stage (100 to 1000) requires different skills. Replacement (or augmentation) at that point is common.
Many people's careers stall not because they failed but because they got promoted past their competence. The honest move is sometimes to step back rather than continue struggling.
The Peter Principle is one of the mental models we apply through real cases inside the Pareto MBA — a part-time program for professionals who want to think clearly about business.