# Pareto principle or 80–20 rule

The Pareto principle (also known as the 80–20 rule, 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. Management consultant Joseph M. Juran suggested the principle and named it after Italian economist Vilfredo Pareto, who observed in 1906 that 80% of the land in Italy was owned by 20% of the population; Pareto developed the principle by observing that 20% of the pea pods in his garden contained 80% of the peas.

It is a common rule of thumb in business; e.g., “80% of your sales come from 20% of your clients”. Mathematically, the 80–20 rule is roughly followed by a power law distribution (also known as a Pareto distribution) for a particular set of parameters, and many natural phenomena have been shown empirically to exhibit such a distribution.

The Pareto principle is only tangentially related to Pareto efficiency. Pareto developed both concepts in the context of the distribution of income and wealth among the population.

## In economics

The original observation was in connection with population and wealth. Pareto noticed that 80% of Italy’s land was owned by 20% of the population. He then carried out surveys on a variety of other countries and found to his surprise that a similar distribution applied.

A chart that gave the inequality a very visible and comprehensible form, the so-called ‘champagne glass’ effect, was contained in the 1992 United Nations Development Program Report, which showed the distribution of global income to be very uneven, with the richest 20% of the world’s population controlling 82.7% of the world’s income.

Distribution of world GDP, 1989
Quintile of population Income
Richest 20% 82.70%
Second 20% 11.75%
Third 20% 2.30%
Fourth 20% 1.85%
Poorest 20% 1.40%

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The distribution is claimed to appear in several different aspects relevant to entrepreneurs and business managers. For example:

80% of a company’s profits come from 20% of its customers
80% of a company’s complaints come from 20% of its customers
80% of a company’s profits come from 20% of the time its staff spend
80% of a company’s sales come from 20% of its products
80% of a company’s sales are made by 20% of its sales staff
Therefore, many businesses have an easy access to dramatic improvements in profitability by focusing on the most effective areas and eliminating, ignoring, automating, delegating or retraining the rest, as appropriate.