The Pareto principle (also known as the 80-20 rule,[1] the law of the vital few, and the principle of factor sparsity) states that, for many events, roughly 80% of the effects come from 20% of the causes.[2][3] Business management thinker Joseph M. Juran suggested the principle and named it after Italian economist Vilfredo Pareto, who observed that 80% of the land in Italy was owned by 20% of the population.[3] It is a common rule of thumb in business; e.g., "80% of your sales come from 20% of your clients." Mathematically, where something is shared among a sufficiently large set of participants, there must be a number k between 50 and 100 such that k% is taken by (100 − k)% of the participants. k may vary from 50 in the case of equal distribution, to nearly 100 when a tiny number of participants account for almost all of the resource. There is nothing special about the number 80% mathematically, but many real systems have k somewhere around this region of intermediate imbalance in distribution.
