It's just the 80:20 rule as applied to income/wealth recursively (20% of 20% of the population has 80% of 80% of the money), as you can see (almost exactly) fro

It's just the 80:20 rule as applied to income/wealth recursively (20% of 20% of the population has 80% of 80% of the money), as you can see (almost exactly) from the wiki chart quoted below.