Pareto’s Law can be summarized as follows: 80% of the outputs result from 20% of the inputs. Alternative ways to phrase this, depending on the context, include: 80% of the consequences flow from 20% of the causes. 80% of the results come from 20% of the effort and time. 80% of company profits come from 20% of the products and customers. 80% of all

Peter Drucker and his book The Effective Executive, as well as Alain de Botton’s (page 486) How Proust Can Change Your Life.