Seems like this would be a natural consequence of the increasing concentration of wealth. The top 1% of the population control 43% of the wealth in the US. But for the 99%, much of that wealth is illiquid and not readily available for investment (particularly speculative investment). So I wouldn't be surprised if the 1% controlled as much as 90% of the liquid wealth available to invest in young companies, making it unnecessary to go to the public markets.