A second cause lies in the fact that fixed-income assets – such as government, corporate, and emerging-market bonds – are not traded in more liquid exchanges, as stocks are. Instead, they are traded mostly over the counter in illiquid markets.
Third, not only is fixed income more illiquid, but now most of these instruments – which have grown enormously in number, owing to the mushrooming issuance of private and public debts before and after the financial crisis – are held in open-ended funds that allow investors to exit overnight. Imagine a bank that invests in illiquid assets but allows depositors to redeem their cash overnight: if a run on these funds occurs, the need to sell the illiquid assets can push their price very low very fast, in what is effectively a fire sale.
Fourth, before the 2008 crisis, banks were market makers in fixed-income instruments. They held large inventories of these assets, thus providing liquidity and smoothing excess price volatility. But, with new regulations punishing such trading (via higher capital charges), banks and other financial institutions have reduced their market-making activity. So, in times of surprise that move bond prices and yields, the banks are not present to act as stabilizers.
In short, though central banks’ creation of macro liquidity may keep bond yields low and reduce volatility, it has also led to crowded trades (herding on market trends, exacerbated by HFTs) and more investment in illiquid bond funds, while tighter regulation means that market makers are missing in action.
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