Myth about 80-20 rule

80-20 rule... Does it sound familiar? Oh, I'm pretty sure that all of us heard about it or even used it in business. There are a lot of incarnations:

• 20% of people owns 80% of world capital.
• 20% of your sales force produces 80% of your company revenue.
• 80% of your outcomes come from 20% of your input.
• 20% of employees makes 80% of work in a company.
• ... and 80% of employees think that they belong to those 20%.
  

and so on.

Internet is full of articles extolling this rule and its variations. I have even seen a series of books promoting a life style that is based on 80-20 principle. And it's good, until readers (and writers, I hope) remember that the figures are fake in most cases... Almost all these rules were declared without even a single statistical analysis!

Someone can say, that I'm trying to mess everything, and these rules are not about the figures, that the rules simply highlights correlation between the least part of input and the major part of output. True... but just sometimes. In other cases the results can be completely different.

Below, there are two statements that deal with the same subject as few rules listed above:

• IT people does NOT spend more than a half of their day doing nothing.
• Healthy IT company does NOT afford itself to have even 25% of useless employees. 75% would simply kill the business.

Does these statements look truthful too?

Pareto principle is great itself. Its mathematical wording is exact. But it is being misused so widely, that I would recommend to think twice before making conclusions on the base of some 80-20 rule, even if it's very popular one.