This rule is discovered by an Italian economist by the name- Vilfredo Pareto.
Hence the rule is also known as the Pareto principle.
I have discovered that laws make success predictable, the whole universe is governed by laws.
The law of least effort or the 80-20 rule states that 80% of your results come from only 20% of your efforts!

In other words, when we live the 80-20 way we can obtain extraordinary results without actually putting in extraordinary efforts.
That is, a small amount of energy...
Read details Here: http://www.tundegold.com/2015/09/the-80-20-rule-doing-less-and-achieving-more.html