Architecture & practice·Estimation and planning
a fifth of the features covered nearly all of the usage, and the rest of the roadmap was the other four fifths.
Pareto principle
Also called80/20 rule
The observation that a small share of causes produces most of the effects. It is useful in prioritisation and in performance work — most latency is usually in a couple of places — and it is dangerous as an excuse, because the last twenty percent of a product is often the part that makes it usable at all. Treat it as a prompt to go and measure the distribution rather than as a licence to stop.