its not exactly 20/80
its a rule of thumb, scientifically and mathematically its not 20/80.
It can range from 30/70, 10/90, 1/99 etc. What it really means is that anomalies or elites are MUCH lesser than the ordinary.
I'm engineer and in project management for consumer machineries and this thing happens throughout everything we do... quality issues ratio, high performers vs average performers, schedule peak vs down time etc.
The 20/80 is the BUZZWORD for it... its not exactly 20/80 as mentioned earlier and it can be controlled in some aspects of life... such as quality issues in mass production, agriculture produce etc. And I study data as part of my role, data science is big these days in my field and its really interesting, but what it falls to is that nothing is perfect and every quantifiable data will show average, mean, median and the pareto principle is just one method to describe things or used as a reference methodology.