Have we reached the limits of monetary¹ policy? No. The central banks’ medicine cabinet is still full. Yet using the old treatments more aggressively or using altogether new treatments creates political, financial and economic risks. Worse, such action cannot solve some of the bigger difficulties the high-income economies confront. In an ideal world, therefore, monetary policy, should not remain “the only game in town”, as the title of a book by the economist² and investment manager Mohamed El-Erian suggests it now is. Unfortunately, we do not live in an ideal world. In the real world, central banks must remain our doctors of choice.

我们已到达货币政策的极限了吗？没有。中央银行的药箱仍是满满的。不过，更激进地使用旧疗法，或者使用全新疗法，都会产生政治、金融和经济风险。更糟糕的是，这么做无法解决高收入经济体面对的一些更大的难题。因此，在理想世界中，货币政策不应继续是“唯一的选择”（经济学家、投资经理穆罕默德•埃尔-埃利安(Mohamed El-Erian)所著《唯一的选择》(The Only Game in Town)的书名暗示，当前情形恰恰如此）。遗憾的是，我们并非生活在理想的世界里。在现实世界中，央行必须继续充当我们的首选医生。

Central banks have duly employed more radical³ treatments than ever before. All the leading central banks of advanced economies have set short-term intervention⁴ rates close to zero. The Bank of Japan has applied⁵ rates this low since 1995. The US Federal Reserve and the Bank of England have used ultra-low rates since early 2009. By 2013, the European Central Bank followed suit — albeit⁶ too slowly.

各国央行已正确地采取了比以往任何时候都要激进的疗法。主要发达经济体的央行都把短期干预利率设置为接近零的水平。自1995年以来，日本央行(BoJ)一直把利率维持在这么低的水平。自2009年初以来，美联储(Fed)和英国央行(BoE)一直采取超低利率政策。到2013年，欧洲央行(ECB)也开始跟进，尽管动作太晚了。

These central banks have also substantially expanded their balance sheets through quantitative⁷ easing or, in the case of the Bank of Japan, “quantitative and qualitative⁸ easing” (which includes lengthening⁹ of the maturity¹⁰ of the assets it buys). Like the Fed, the Bank of England has stopped purchasing assets. But its balance sheet is bigger, relative to UK gross domestic product, than throughout its long history. The BoJ and ECB are still expanding their balance sheets today (see charts).

这些央行还通过量化宽松——日本央行则采取“量化兼质化宽松”（包括延长所购资产的期限）——大幅扩大了自己的资产负债表。与美联储一样，英国央行已停止购买资产。但是，英国央行资产负债表相对英国国内生产总值(GDP)的比例，已达其史上最高。日本央行和欧洲央行目前仍在扩大自身资产负债表（参见图表）。

More recently, as Mark Carney, governor of the Bank of England, noted¹¹ in Shanghai in February: “Central bank innovation has … extended to negative rates, with around a quarter of global output produced in economies where policy rates are literally¹² through the floor.”

正如英国央行行长马克•卡尼(Mark Carney) 2月在上海所指出的：“央行的创新已……扩展到负利率，全球产出中大约有四分之一是政策利率低于零的经济体创造出来的。”

Yet, even after years of such effort, the US is the only significant high-income economy to have achieved its target rate of core consumer price inflation. That is also why the Fed alone has started a tightening¹³ cycle, albeit in a gingerly fashion, with the federal funds rate still below 0.5 per cent.

然而，即便经过多年的如此努力，美国仍是唯一实现核心消费价格通胀率目标的重要高收入经济体。也正因为如此，唯有美联储启动了紧缩周期，不过动作小心翼翼，联邦基金利率现在仍低于0.5%。

One response to this apparent failure is the argument that hitting the inflation target does not matter. Some even argue that deflation has merits. This view is flawed, for three reasons.

针对这一明显失败，有人提出了达成通胀率目标并不重要的观点。有些人甚至辩称，通缩也有好处。这一看法是错误的，原因有三。

First, if inflation is zero or, still worse, if it turns negative, it becomes harder to secure needed changes in relative prices and wages. The obstacle here is nominal¹⁴ wage rigidity¹⁵. This difficulty is particularly important in a multi-country currency union, such as the eurozone.

第一，如果通胀率为0，或者更糟，通胀率变为负值，那么我们将更难实现相对物价和工资的必要变化。这里的障碍是名义工资刚性。这一难题在欧元区这样的多国货币联盟尤为突出。

Second, under deflation negative real interest rates are possible only with strongly negative nominal interest rates. Without negative real interest rates, countries might end up in a prolonged period of deficient¹⁶ demand, elevated unemployment and weak investment.

第二，在通缩情况下，只有显著低于零的名义负利率才能产生实际负利率。若没有实际负利率，各国或许最终会陷入更长期的需求不足、失业率升高和投资不振。

Third, under deflation the real burden implied by a given level of nominal debt spirals upwards¹⁷. This risks creating “debt deflation”, a condition explained by the US economist, Irving Fisher, in the 1930s. While Japan managed to stabilise deflation at a slow rate, this may be due to its aggressive use of fiscal¹⁸ policy. With the latter ruled out in the eurozone, the risks of accelerating deflation might be even greater there.

第三，在通缩情况下，给定水平名义债务所隐含的实际债务负担会螺旋式上升。这就可能产生“债务通缩”，美国经济学家欧文•费雪(Irving Fisher)在1930年代解释过这种情况。尽管日本成功地把通缩稳定在低水平上，但这可能是该国积极使用财政政策的结果。由于欧元区排除了财政政策，那里通缩加速的风险或许会更高。

It is important, then, for central banks to hit their inflation targets. This entails¹⁹ very low, or even negative, nominal rates. As Mario Draghi, president of the ECB, explained in a recent speech, many complain that these low interest rates are themselves the problem. “But,” he responds, “they are not the problem. They are the symptom of an underlying²⁰ problem, which is insufficient²¹ investment demand, across the world, to absorb all the savings²² available in the economy.”

因此，央行达成通胀率目标非常重要。这需要很低、甚至负值的名义利率。正如欧洲央行行长马里奥•德拉吉(Mario Draghi)在不久前一次演讲中所解释的那样，许多人抱怨称，低利率本身就是问题所在。“但是，”他回答说，“低利率本身并不是问题，而是另一个深层次问题的表象，那就是全球投资需求不足，无法吸收经济中的全部储蓄。”

The question is how well monetary policy can remedy such a chronical deficiency in demand. One answer is that central banks possess many ways of delivering further monetary stimulus²³: low and even negative interest rates, asset purchases, forward guidance, higher inflation targets, outright²⁴ monetary financing of government deficits²⁵, and direct dispatch of money to households.

问题在于，货币政策能在多大程度上解决长期需求不足的难题。一个答案是，央行拥有提供进一步货币刺激的多种手段：低利率甚至负利率、资产购买、前瞻指引、提高通胀率目标、直接为政府赤字提供货币融资，以及直接向家庭派发现金。

In recent blogs, Ben Bernanke, former chairman of the Fed, demonstrates the potency²⁶ of such tools. He could even be too cautious about how low negative rates can go, arguing that “beyond a certain point, people will just choose to hold currency, which pays zero interest”. But creating a payment system based on cash is a difficult and expensive task. More fundamentally, as Martin Sandbu has argued, it would be possible for the central bank or the banks to limit access to cash or impose charges on converting deposits into cash. Some economists²⁷ even recommend abolishing cash.

在不久前的博客文章中，美联储前主席本•伯南克(Ben Bernanke)阐释了这些工具的强大作用。对于负利率可能低到什么程度，他甚至可能太过谨慎了，他说，“超过某个临界点后，人们将选择持有货币，利率为零”。但是，创建一种基于现金的支付系统，是一项艰难且成本高昂的任务。更根本的问题是，正如马丁•桑德布(Martin Sandbu)所指出的那样，央行或普通银行有可能限制人们取现、或者对存款取现收费。有些经济学家甚至建议取消现金。

Nevertheless, going further does run into significant difficulties.

不过，进一步采取货币政策的确会遇到重大困难。

First, the more unconventional the policy, the more difficult it is to calibrate²⁸ its effects. It is necessary to create just enough additional demand, but not too much, along with manageable side effects. This is quite hard to do, not least because monetary policy works via many channels. Moreover, the effects can be unpredictable. Do negative rates, for example, increase confidence by showing that central banks are not out of ammunition²⁹, or damage it by proving how bad the illness is?

第一，货币政策越是非常规，衡量其效果的难度越大。有必要创造刚好足够的额外需求，但又不能创造太多需求，同时要让副作用处于可控范围。做到这一点是相当困难的，重要原因在于，货币政策是通过多条渠道发生作用的。另外，影响可能是不可预测的。比如说，负利率到底会因表明央行并未耗尽弹药而增强信心，还是会因证明病症有多么严重而削弱信心？

Second, some remedies might be worse than the disease. Perhaps the biggest concern is that extreme monetary policy risks distorting asset prices and generating new financial bubbles. Another critique is that reliance on monetary policy treatmentsrelieves pressure on governments to conduct necessary structural³⁰ reforms. Again, policies apparently³¹ designed to affect the exchange rate could be viewed as beggar-my-neighbour devices.

第二，有些疗法或许会比疾病更有害。最令人担心的或许是，极端货币政策可能扭曲资产价格，并引发新的金融泡沫。另一种批评是，依赖货币政策疗法会减轻政府执行必要结构性改革的压力。此外，明显旨在影响汇率的政策可能被视为以邻为壑的勾当。

Third, extreme monetary policy runs into political objections. Creditors³² object to all policies aimed at lowering interest rates, for example. Again, people fear that direct financing of government deficits would merely encourage fiscal profligacy³³.

第三，极端货币政策会遇到政治障碍。比如说，债权人反对一切旨在降息的政策。此外，人们担心，直接为政府赤字提供货币融资将只会助长财政挥霍。

Apart from these objections, there are two other important difficulties with heavy reliance on monetary policy.

除这三点外，严重依赖货币政策还有两大难题。

One of these is that, if the fundamental difficulty is an excess of savings over investment, fiscal policy would be a better targeted remedy. In Japan, for example, the great difficulty has been the excess savings of the non-financial corporate³⁴ sector³⁵. The obvious remedy would be higher taxation³⁶ of retained profits. Higher taxation of consumption is simply misdirected. An alternative would be for governments to increase spending on high-priority public investments.

其一是，如果根本难题在于储蓄相对于投资过剩，那么财政政策将是更有针对性的对策。比如，在日本，非金融企业部门的储蓄过高一直是个重大难题。显而易见的对策是提高对留存收益的征税。提高消费税完全是误入歧途。替代方案将是，政府增加在优先公共投资项目上的支出。

Another objection is that weakness of demand is not the sole difficulty. At least as important is declining growth of productivity and, in a number of countries, the inflexibility³⁷ of markets. For such reasons, a more complete package should include structural reforms. The latter are not a panacea³⁸, particularly in the short term, as theInternational Monetary Fund has noted. But they need to be a part of the mix.

另一条反对理由是，需求不足并非唯一难题。至少同样重要的难题，是生产率提高的速度在放缓，以及许多国家存在的市场不灵活。出于此类原因，一个更全面的解决方案应当包括结构性改革。正如国际货币基金组织(IMF)所指出的那样，结构性改革不是万灵丹，尤其在短期内不是。但是，需要把结构性改革作为政策组合的一部分。

Monetary policy is not exhausted³⁹, and active use of it is essential. But undue⁴⁰ reliance on monetary policy is problematic.

货币政策并未用尽，积极采用货币政策是不必可少的。但不适当地依赖货币政策，则会带来问题。

One difficulty lies in the political limits to further action. Another limitation is the need to calibrate policy and mitigate⁴¹ side effects. Fiscal policy should play a far bigger part in demand management. More importantly, monetary policy can palliate, but not cure, structural problems of low growth and inflexible⁴² markets. We still need active monetary policy. But it is not all we need

一个难点是，采取进一步的货币政策面临政治障碍。另一个障碍是，需要衡量政策、并减弱副作用。财政政策应在需求管理中扮演重要得多的角色。更重要的是，货币政策只能减轻、而不能治愈增长率低和市场不灵活的结构性问题。我们仍需要积极的货币政策。但货币政策并非我们需要的全部。