I meant the "Pareto principle"[0], or 80-20 rule, that says that you can get 80% of effect with 20% of work. If you apply the rule to itself, you get the 64-4 rule, and if you do this again, you get 51.2% of results from 0.8% of work ;).

[0] - http://en.wikipedia.org/wiki/Pareto_principle.