The 80-20 rule, also known as the Pareto Principle, is a familiar saying that asserts that 80% of outcomes (or outputs) result from 20% of all causes (or inputs) for any given event. In business, a goal of the 80-20 rule is to identify inputs that are potentially the most productive and make them the priority. For instance, once managers identify factors that are critical to their company's success, they should give those factors the most focus.