First, while my example above is extreme, the problem with even 20% of the market being “passive” is the liquidity issues surrounding the market as a whole. With more ETF’s than individual stocks, and the number of outstanding shares traded being reduced by share buybacks, the risk of a sharp and disorderly reversal remains due to compressed credit and liquidity risk premia. As a result, market participants need to be mindful of the risks of diminished market liquidity, asset price discontinuities and contagion across asset markets.
