Pareto's rule

Originally a rule applied to income distribution by Italian economist Vilfredo Pareto. Pareto stated that 80% of a nation's income would only benefit 20% of the population. This principle was subsequently extended to a range of other examples such as 80% of a company's profits coming from 20% of its products or services, or 80% of a company's computer problems stemming from 20% of its machines.