The pareto principle

The Pareto principle state that 80% of the consequences comes usually from 20% of the causes. This can be applied in many areas (not sure about real evidence, so don't take this as a corollary).

The bottom line is that we should look for that 20% of effort that will yield 80% of the results. Whatever that means.

https://en.wikipedia.org/wiki/Pareto_principle

This is somewhat similar to 202106031349 The barbell strategy (not quite, but it stays at the same conceptual goo for me)