Pareto Principle

a.k.a. the 80-20 rule

The business truism, also known as the "80-20 rule," in which 80% of your business comes from 20% of your customers. Vilfredo Pareto, the 19th-century economist who coined the term, would most likely have to revise it for the 21st century since the harsh reality today is that the split tends to be closer to 90%-10% or even 95%-5%.

See also : critical mass  
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