QE: a successful start may be running into diminishing returns
现有研究可能低估了首轮量化宽松对英国GDP的正面影响，但后续轮次因银行惜贷和国债收益率已处历史低位而效果递减，甚至可能产生负回报。
Existing studies may have underestimated the impact of QE1 on UK GDP because they did not take full account of the beneficial effect on credit risk spreads and on the exchange rate. However, all such effects were also influenced by the roughly simultaneous introduction of similar easing in the USA, which complicates the analysis. Another area where QE has been positive is in reducing public-sector borrowing costs. Where QE1 (and subsequent rounds) have disappointed is in their inability to stimulate a recovery in credit and monetary growth, amid an increased desire among banks to hold far more of their reserves at the central bank. Moreover, there is growing evidence of significant diminishing returns in QE2 as gilt rates have already fallen to historically low levels and the risk is that, if policy-makers fail to resuscitate the bank lending channel, further rounds of QE could potentially have negative returns.