Wikipedia summarizes the Pareto Principle like this:

The Pareto principle (also known as the 80-20 rule, the law of the vital few and the principle of factor sparsity) states that, for many events, 80% of the effects comes from 20% of the causes.

To some people, this seems to suggest:

20% efforts => 80, 90, 99% results! WOW!

It is easy to fool yourself into believing all that matters were those 20%. Once you believe that, however, the Pareto Principle becomes kind of a voodoo ritual:  » Read more