Yes. 199billion dollars ago. If he collected and hoarded anything else except money, he would be considered mentally ill. Well, I consider all multi-billionaires to be sociopaths, but you know what I mean
Capital in the 21st Century by Thomas Piketty
...central thesis is that when the rate of return on capital (r) is greater than the rate of economic growth (g)... the result is concentration of wealth, and this unequal distribution of wealth causes social + economic instability.