From Longman Business DictionaryPareto's LawPaˈreto’s ˌLaw (also Pareto’s principle), Pareto’s rule nounECONOMICS the idea that a small part of something is responsible for a large part of its value. For example, 20% of the work people do produces 80% of the rewards. It is also sometimes called the 80/20 ruleIf you are a manufacturer, you can use Pareto’s Law to evaluate whether to add to or eliminate part of your product line.