Why are interest rates so low? The best answer is that the advanced countries are still in a “managed depression”. This malady is deep. It will not end soon.
当前利率为何如此之低？最佳答案是，发达国家仍处于一种“可管理的萧条”之中。这种萧条非常严重，它不会很快结束。
One can identify three different respects in which interest rates on “safe” securities in the principal high-income monetary areas (the US, the eurozone, Japan and the UK) are exceptionally low. First, the short-term intervention rates of central banks are 0.5 per cent or lower. Second, yields on conventional long-term government bonds are extremely low: the German 30-year bond yields 0.7 per cent, the Japanese close to 1.5 per cent, the UK 2.4 per cent and the US 2.6 per cent. Finally, long-term real interest rates are minimal: UK index-linked 10-year gilts yield minus 0.7 per cent; US equivalents yield more, but still only plus 0.4 per cent.
人们可以发现，主要高收入货币区（美国、欧元区、日本和英国）的“安全”证券利率异常低表现在三个不同方面。首先，央行的短期干预利率是0.5%甚至更低。其次，长期政府债券的收益率极低：德国30年债券收益率为0.7%，日本接近1.5%，英国是2.4%，美国是2.6%。最后，长期实际利率也非常低：英国十年期通胀挂钩国债收益率为-0.7%，美国同类债券收益率高一些，但也只有0.4%。

If you had told people a decade ago that this would be today’s reality, most would have concluded that you were mad. The only way for you to be right would be if demand, output and inflation were to be deeply depressed — and expected to remain so. Indeed, the fact that vigorous programmes of monetary stimulus have produced such meagre increases in output and inflation indicates just how weak economies now are.
如果你在十年前告诉人们，今天会出现上述这些情况，大多数人会认为你疯了。只有需求、产出和通胀全都极度低迷，并且人们预期这种低迷还会持续下去，你的预言才有可能成真。实际上，力度极大的货币刺激措施给产出和通胀带来的增幅非常小，可见当前经济多么疲弱。
Yet today we hear a different explanation for why interest rates are so low: it is the fault of monetary policy — and especially of quantitative easing, the purchase of long-term assets by central banks. Such “money printing” is deemed especially irresponsible.
然而，现在我们听到了关于利率极低的不同解释：它是货币政策（尤其是央行购买长期资产这类量化宽松政策）的错。有些人认为此类“印钞行为”特别不负责任。
As Ben Broadbent, deputy governor of the Bank of England, has argued, this critique makes little sense. If monetary policy had been irresponsibly loose for at least six years — let alone, as some have argued, since the early 2000s — one would surely have seen inflationary overheating, or at least rising inflation expectations. Moreover, central banks cannot set long-term rates wherever they wish. Empirical analysis of the impact of quantitative easing suggests it might have lowered bond yields by as much as a percentage point. But note that yields remained extremely low even well after QE ended, first in the UK and now in the US.
正如英国央行(Bank of England)副行长本•布罗德本特(Ben Broadbent)所说的，这种指责毫无道理。如果货币政策在至少6年时间里——还有些人说是自本世纪初以来——保持一种不负责任的宽松，人们肯定会看到通胀飙升，或者至少是通胀预期不断上升。此外，央行不可能随心所欲地制定长期利率。对量化宽松效果的实证分析表明，它可能将债券收益率拉低了1个百分点。但请注意，即便在量化宽松政策结束之后（先是英国，现在是美国），收益率依然保持了极低的水平。
The price level is the economic variable that monetary policy influences most strongly. Central bankers cannot determine the level of real variables — such as output, employment, or even real interest rates (which measure the return on an asset after adjusting for inflation). This is especially true over the long run. Yet the slide in real interest rates is longstanding. As measured by index-linked gilts, they fell from about 4 per cent before 1997, to about 2 per cent between 1999 (after the Asian financial crisis) and 2007, and then towards zero (in the aftermath of the western financial crisis).
物价水平是受货币政策影响最明显的经济变量。央行家们不可能决定实际经济变量的水平，比如产出、就业，甚至是实际利率，后者衡量的是经通胀调整后的资产回报率。长期而言尤其如此。然而实际利率的下降是长期性的。以通胀挂钩债券衡量，它们的收益率从1997年以前的4%左右，降至1999年（亚洲金融危机爆发之后）至2007年间的2%左右，随后又降至接近零的水平（西方金融危机爆发之后）。
There is a more convincing story about why interest rates are so low. It is that the equilibrium real interest rate — crudely, the interest rate at which demand matches potential supply in the economy as a whole — has fallen, and that central bankers have responded by cutting the nominal rates they control. Lawrence Summers, former US Treasury secretary, has labelled the forces “secular stagnation” — by which is meant a tendency towards chronically deficient demand.
利率极低的原因有更令人信服的解释。那就是，均衡实际利率——简单地说，就是整体经济中需求与潜在供给相匹配时的利率——已经下降，央行行长通过降低他们控制的名义利率来应对。美国前财政部长劳伦斯•萨默斯(Lawrence Summers)将这种状况称为“长期停滞”(secular stagnation)，意指长期性需求不足的趋势。
The most plausible explanation lies in a glut of savings and a dearth of good investment projects. These were accompanied by a pre-crisis rise in global current account imbalances and a post-crisis overhang of financial stresses and bad debt. The explosions in private credit seen before the crisis were how central banks sustained demand in a demand-deficient world. Without them, we would have seen something similar to today’s malaise sooner.
最合理的解释是储蓄过剩和缺乏良好的投资项目。伴随着这些问题，金融危机前全球经常账户失衡加剧，危机后金融压力和不良债务问题严重。危机前出现的私人信贷激增，显示了在一个需求不足的世界，央行怎样维持需求。如果不是它们，我们会更早看到与今日类似的低迷景象。
Since the crisis, central banks have not chosen how to act — their hands have been forced. Events in the eurozone provide a powerful example. In early 2011, the European Central Bank raised its intervention rate from 1 to 1.5 per cent. This was wildly inappropriate, and in the end the ECB had to cut rates again and embark on QE. If central banks are to be a stabilising force, they have to move interest rates in an equilibrating direction — and that direction is not something they can choose.
危机爆发以来，各国央行没有选择如何行动——它们的手一直被压着。欧元区发生的事提供了一个有力例证。2011年初，欧洲央行(European Central Bank)将干预利率从1%上调到1.5%。此举极为不妥，欧洲央行最后不得不再次降息，并开始采取量化宽松。如果央行想成为一个起到稳定作用的力量，它们就得按照一个平衡的方向调整利率——而这个方向还不是它们能选择的。
Rising risk aversion might be another reason why real interest rates on safe securities have fallen. The idea is that the crises increased the appeal of the safest and most liquid assets. This is part of the explanation for ultra-low yields on German Bunds. But it does not seem to be the dominant explanation over the longer run. The gap between the interest rate on treasuries and US corporate bonds has not been consistently wider since the crisis, for example.
厌恶风险心理加重可能是安全证券实际利率出现下降的另一个原因。因为金融危机增加了最安全以及流动性最强的资产的吸引力。这在一定程度上解释了为什么德国国债的收益率极低。但从长期角度来看，这似乎不是一个主要因素。比如自金融危机以来，美国国债和企业债券之间的息差并不是一直都比较大。
We should view central banks not as masters of the world economy, but as apes on a treadmill. They are able to balance demand with potential supply in high-income countries only by adopting ultra-easy policies that have destabilising consequences down the line.
我们不该将央行看作是全球经济的主宰，而应将它们看成在一台跑步机上奔跑的猩猩。它们只有采用超宽松的政策，才能在高收入国家平衡潜在供给与需求之间的关系，但这些政策会在各个方面产生不稳定的后果。
When will we see an enduring rise in real and nominal interest rates? That would require a marked strengthening of investment, a marked fall in savings and a marked decline in risk aversion — all unlikely in the near future. China is slowing, which is likely to depress interest rates further. Many emerging economies are also weakening. The US recovery might not withstand significantly higher rates, particularly given the dollar’s current strength. Debt also remains high in many economies.
什么时候我们才能看到实际利率和名义利率出现持续上升？这将需要投资明显加强，储蓄明显减少以及避险意识明显下降，所有这些在近期都不大可能发生。中国经济正在放缓，这很可能进一步抑制利率。许多新兴经济体也在变得疲弱。美国的经济复苏可能无法承受利率大幅提高，尤其是考虑到美元目前的强势。许多经济体的债务负担仍很重。
Ultra-low interest rates are not a plot by central bankers. They are a consequence of contractionary forces in the world economy. While upward moves in rates seem ultimately inevitable from current levels, it is likely that historically low rates will be with us for quite a while. Those who bet on jumps in inflation and a bond-market rout will continue to be disappointed. The depression has been contained. But it is a depression, all the same.
超低利率不是央行的阴谋，而是紧缩性力量在全球经济中制造的后果。虽然利率上行最终是不可避免的，但处在历史低点的利率很可能将伴随我们很长一段时间。那些打赌通胀会飙升、债券市场会崩溃的人仍将失望。萧条已经得到了遏制，但萧条毕竟是萧条。