Universal Principles of Design, Revised and Updated

80/20 Rule

A high percentage of effects in any large system are caused by a low percentage of variables.1

The 80/20 rule asserts that approximately 80 percent of the effects generated by any large system are caused by 20 percent of the variables in that system. The 80/20 rule is observed in all large systems, including those in economics, management, user interface design, quality control, and engineering, to name a few. The specific percentages are not important, as measures of actual systems indicate that the proportion of critical variables varies between 10 percent and 30 percent. The universality of the 80/20 rule suggests a link to normally distributed systems, which limits its application to variables that are influenced by many small ...