A paradox has emerged in the financial markets of the advanced economies since the 2008 global financial crisis. Unconventional monetary policies have created a massive overhang of liquidity. But a series of recent shocks suggests that macro liquidity has become linked with severe market illiquidity.

Policy interest rates are near zero (and sometimes below it) in most advanced economies, and the monetary base (money created by central banks in the form of cash and liquid commercial-bank reserves) has soared – doubling, tripling, and, in the United States, quadrupling relative to the pre-crisis period. This has kept short- and long-term interest rates low (and even negative in some cases, such as Europe and Japan), reduced the volatility of bond markets, and lifted many asset prices (including equities, real estate, and fixed-income private- and public-sector bonds).

And yet investors have reason to be concerned. Their fears started with the “flash crash” of May 2010, when, in a matter of 30 minutes, major US stock indices fell by almost 10%, before recovering rapidly. Then came the “taper tantrum” in the spring of 2013, when US long-term interest rates shot up by 100 basis points after then-Fed Chairman Ben Bernanke hinted at an end to the Fed’s monthly purchases of long-term securities.

Likewise, in October 2014, US Treasury yields plummeted by almost 40 basis points in minutes, which statisticians argue should occur only once in three billion years. The latest episode came just last month, when, in the space of a few days, ten-year German bond yields went from five basis points to almost 80.

These events have fueled fears that, even very deep and liquid markets – such as US stocks and government bonds in the US and Germany – may not be liquid enough. So what accounts for the combination of macro liquidity and market illiquidity?

Read more at http://www.project-syndicate.org/commentary/liquidity-market-volatility-flash-crash-by-nouriel-roubini-2015-05#geBgIRRGDygg19rf.99

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