The top 10% of the population in the us own 70% of everything that can be owned. Here is a model explaining how this could occur.
http://www.dailypaul.com/111232/us-wealth-distribution-10-of-us-citizens-own-709-of-all-us-assetsThree University of Minnesota researchers have built a simplified model that isolates the effects of chance and found that it consistently pushes wealth into the hands of a few, ever-richer people.
The researchers simulated the performance of a large number of investors who started out with equal amounts of capital and who realized returns annually over a number of years. But wealth did not remain equal, because each year an entrepreneur's return was a random draw taken from a pool of possible return rates. Thus, a high return did not guarantee continuing high returns, nor did early low returns mean continuing bad luck.
Even though all investors had an equal chance of success, the simulations consistently resulted in dramatic concentration of wealth over time. The reason: With compounding capital returns, some individuals will have a string of high returns and, given enough time, will accumulate an overwhelming share of the wealth.
The model predicts that the rate at which wealth concentrates depends on the variation among individual return rates. For example, when variation is high, it would take only 100 years for the top 1 percent to increase their share of total wealth from 40 percent -- a recent level in the United States -- to 90 percent.
Chance Favors the Concentration of Wealth, Study Shows; New Model Isolates the Effects of Chance in an Investment-Based Economy