Vilfredo Pareto was an Italian Economist who noticed that, among other things, a minority of the pea crop in his garden produced the majority of the peas. A Pareto Analysis (also known as 80/20 Analysis) identifies the "Critical Few" people and/or things that are the most productive.
For example, 80% of sales are closed by 20% of salespeople on the sixth callback. 80% of sales also come from 20% of your customers, who buy 20% of your key products or services. 80% of your own personal productivity occurs 20% of the time. 80% of bank deposits are owned by 20% of depositors, and so on.