80/20 rule expression (Pareto Principle)


Is there a saying (ことわざ）or 4 character phrase (四字熟語) in Japanese for the 80-20
rule (i.e. the Pareto Principle)? i.e. it takes 20% of the effort to get 80%
of the results but to get the last 20% of the results takes 80% of the effort.




What you describe is also known in English as the Pareto principle.

From this site <https://takuminotie.com/blog/2015/09/09/post-9226/>

we have the usage

> パレートの法則

The site also says that...

> それで、これらは俗に80対20の法則、2：8の法則、80-20ルールとも呼ばれる。

