Though $3.6 trillion of incremental liquidity has been added to the Fed’s balance sheet since late 2008, nominal GDP was up by just $2.5 trillion from the third quarter of 2008 to the second quarter of this year. As John Maynard Keynes famously pointed out after the Great Depression, when an economy is locked in a “liquidity trap,” with low interest rates unable to induce investment or consumption, attempting to use monetary policy to spur demand is like pushing on a string.
美联储流动性注入所产生的“GDP红利”严重低迷也印证了这一点。自2008年末以来，美联储资产负债表上增加了3.6万亿美元流动性，但自2008年三季度到今年二季度，名义GDP只增长了2.5万亿美元。凯恩斯在大萧条后曾指出，当经济陷入“流动性陷阱”，即低利率无法刺激投资和消费时，试图使用货币政策提振需求就好比是想推着绳子前进。