The term pareto is from 1920, in reference to the work of Italian economist Vilfredo Federico Pareto (1848-1923). The pareto principle (also known as the 80/20 rule, the law of the vital few, or the principle of factor sparsity) states that, for many events, roughly 80% of the effects come from 20% of the causes. For inventory, approximately 80% of the turnover (stock etc.) can be ascribed to approximately 20% of the customers, articles or orders. The actual ratio in a particular case can be determined by ranking the customers and products etc. in order of magnitude and then calculating what percentage of the turnover (stock etc.) corresponds to 10%, 20% 30% etc. of the customer and products etc. What 20% of anything drives 80% of everything?