As a result, when surprises occur – for example, the Fed signals an earlier-than-expected exit from zero interest rates, oil prices spike, or eurozone growth starts to pick up – the re-rating of stocks and especially bonds can be abrupt and dramatic: everyone caught in the same crowded trades needs to get out fast. Herding in the opposite direction occurs, but, because many investments are in illiquid funds and the traditional market makers who smoothed volatility are nowhere to be found, the sellers are forced into fire sales.
This combination of macro liquidity and market illiquidity is a time bomb. So far, it has led only to volatile flash crashes and sudden changes in bond yields and stock prices. But, over time, the longer central banks create liquidity to suppress short-run volatility, the more they will feed price bubbles in equity, bond, and other asset markets. As more investors pile into overvalued, increasingly illiquid assets – such as bonds – the risk of a long-term crash increases.
This is the paradoxical result of the policy response to the financial crisis. Macro liquidity is feeding booms and bubbles; but market illiquidity will eventually trigger a bust and collapse.
Read more at http://www.project-syndicate.org/commentary/liquidity-market-volatility-flash-crash-by-nouriel-roubini-2015-05#83lHDggqLzZFGBpP.99