Virtually every business seeks to increase its profit, but few business leaders realize that a universal law governs profit from customers. You may be applying the 80/20 rule to sales, quality control, investing, or production, without realizing that this rule summarizes the Pareto distribution of inputs to outputs. The 80/20 rule predicts that the top 20% of inputs generate 80% of the outputs, balanced by the bottom 80% of inputs generating 20% of the outputs.