См.: Принцип Парето.
Pareto principlePareto principle - - A principle that states that for many phenomena approximately 80% of the effects result from 20% of the causes.
Perspective: An Italian economist, Vilfredo Pareto, studied the distribution of wealth in Italy and found that less than 20% of the population owned 80% of the country's wealth. It has been found that this principle holds in many environments: for example 20% of inventory items account for 80% of inventory investment and 80% of defects are due to 20% of causes. Goldratt states that although the Pareto principle applies to independent items, dependency exists in most situations. For dependent items he believes that the ratio of effects to causes is much higher than 80 to 20. For example, .1% of items may cause 99.9% of effects when there is a high degree of dependency.