The Pocket Universal Principles of Design

002 80/20 Rule

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

• Proposed by the economist Vilfredo Pareto, who observed that 20 percent of the Italian people possessed 80 percent of the wealth.

• Applying the 80/20 rule means identifying and focusing resources on the critical 20 percent. Focusing on aspects of a design beyond the critical 20 percent yields diminishing returns.

• For example, 80 percent of a product’s usage involves 20 percent of its features; 80 percent of a product’s bugs are caused by 20 percent of its components.

• Use the 80/20 rule to assess the relative value of elements, target areas of redesign and optimization, and focus resources in an efficient manner. Note that 80/20 is ...