A flattened curve 变平的曲线

2020年9月


Why does low unemployment no longer lift inflation?
低失业率为何不再推高通胀?【“反思经济学基本理论”系列之三】 

 

A flattened curve 变平的曲线


EVERY NIGHT at about 10pm the lights of the prisoner-of-war camp in Indonesia would mysteriously dim, to the puzzlement of the Japanese guards. They failed to spot the makeshift immersion heaters, used to brew cups of tea for the inmates, that had been cobbled together by a prisoner from New Zealand, William Phillips. These secret contraptions were just one example of his resourcefulness.
每晚到了十点左右,印度尼西亚一个战俘营的灯光都会神秘地暗下来,日本看守们对此百思不得其解。他们没有发现那些简易“热得快”——由来自新西兰的囚犯威廉•菲利普斯(William Phillips)捣鼓出来给狱友们泡茶用。这批秘密的小玩意只是他聪明才智的例证之一。
After the second world war he built a “hydraulic” model of the circular flow of income in an economy—a labyrinth of water tanks, valves and pipes that helped earn him an appointment at the London School of Economics. But neither of these exploits is the reason why Phillips is known to every economist today. His fame rests instead on his “quick and dirty” study, published in 1958, documenting a striking, decades-long relationship between British wage inflation and unemployment: the one tended to be high when the other was low. A downward-sloping curve, which he drew largely freehand, illustrated the point. The Phillips curve, as it became known, has been described as “probably the single most important macroeconomic relationship”. It has also been called the “least solid piece of work” he ever did.
二战后,他建了一个“液压”模型来论证经济体中收入的循环流动。这个由水箱、阀门和管道组成的迷宫帮他谋得了伦敦经济学院(London School of Economics)的一个职位。但上述两样成果都不是今天所有经济学家都知道菲利普斯其人的原因。他的赫赫声名建基于他在1958年发表的一项“潦草”的研究,记录了英国工资上涨与失业率之间长达数十年的惊人关联:当一个走低时,另一个趋于走高。他用一条基本上是徒手绘制的向下倾斜的曲线阐明了这一点。这条后来变得众所周知的“菲利普斯曲线”被描述为“很可能是最重要的宏观经济关系,没有之一”。它也被称为是菲利普斯做过的“最不可靠的研究”。
The Phillips curve’s solidity and shape has been called into question more than once in the past 60 years, including in the period since the global financial crisis of 2007-09. But the logic of the curve still guides central banks today.
菲利普斯曲线的可靠性和形状在过去60年里不止一次引发质疑,包括自2007到2009年全球金融危机以来的这些年。但这条曲线的逻辑仍然指导着今天的央行。
When business is brisk and unemployment low, central bankers worry that workers will demand pay raises over and above inflation and any improvement in their productivity. If firms pass these higher wages on to customers by increasing prices, inflation will rise. If central bankers wish to prevent this, they will raise the interest rate they charge for the money they lend, slowing the economy and curbing the wage pressure.
当经济活跃、失业率走低时,央行官员们担心工人要求涨薪的幅度会超过通胀和其生产率提升的幅度。如果企业通过涨价把工资增长转嫁给客户,通胀将上升。如果央行官员希望避免这种情形,他们将提高贷款利率来放缓经济增速并抑制工资的上行压力。
The opposite happens at the other end of the curve. High unemployment flattens wages and spending, putting downward pressure on inflation. To counteract this, policymakers typically cut interest rates.
在曲线的另一端,发生的情况正相反。高失业率压低工资和支出,给通胀带来下行压力。为对抗这种压力,政策制定者通常会降低利率。
Central bankers hope to find themselves somewhere in the middle: with inflation where they want it to be and unemployment neither high nor low enough to dislodge it. In these happy circumstances, they aim to set a “neutral” interest rate that will leave inflation where it is.
央行官员希望置身于中间的某个地方:通胀处在他们想要的水平,而失业率没有高到或低到影响通胀的程度。在这样令人愉悦的情形下,他们的目标是设定一个“中性”利率,以让通胀保持在原位。
Most central banks in the rich world target an
inflation rate of about 2%. At such modest levels, inflation does not greatly complicate financial planning or erode confidence in the currency. But it allows wages to fall modestly, relative to prices, without anyone suffering a thinner pay packet. That cheapening of labour may, in turn, help preserve jobs in a downturn.
多数富裕国家的央行把通胀目标设在2%左右。这样的些许通胀不会让财务规划过于复杂,也不会削弱人们对货币的信心。但它允许工资相对于物价略微下降,而每个人的工资袋却不会变薄。劳动力成本的下跌继而可能在经济低迷期帮助保住工作岗位。
In recent years, however, inflation has fallen persistently short of the central bank’s target in many countries (see chart). In the immediate aftermath of the global financial crisis, such low inflation was no puzzle. Unemployment rose sharply, reaching 10% in America in October 2009. In those circumstances, the only surprise was that inflation did not fall further. But after the recovery inflation continued to remain muted even as unemployment in America, the euro area and Japan fell unusually far. That has forced economists to rethink the relationship.
然而,近些年许多国家的通胀率一直都低于央行的目标(见图表)。在全球金融危机刚发生后的时期里,这样的低通胀不足为奇。失业率急剧上升,2009年10月在美国已经达到10%。在这种情况下,唯一的意外是通胀率没有下跌更多。但是,经济复苏后,即便美国、欧元区和日本的失业率回落到异常低位,通胀却仍没什么动静。这迫使经济学家重新思考两者的关系。 


In the 1960s some sceptics, perhaps most notably Milton Friedman, pointed out that the relationship between unemployment and inflation is only as solid as the expectations that underlie it. If inflation is expected to be 2%, then workers emboldened by low unemployment might demand a wage increase of 3 or 4%. But if inflation is expected to be 10%, then similarly emboldened workers might demand a wage increase of 11% or more. In the 1970s, high inflation persisted despite high unemployment precisely because workers’ expectations of inflation had risen so much. Economists decided to “augment” the Phillips curve by adding expectations alongside unemployment as a separate determinant of inflation.
在1960年代,一些质疑者(米尔顿•弗里德曼可能是其中最出名的一个)指出,失业率和通胀率关联的程度要看人们对这种关联的预期程度。如果人们预期通胀率为2%,那么受到低失业率鼓舞的工人可能会要求加薪3%或4%。但如果预期通胀率为10%,那么受低失业率鼓舞的工人可能会要求加薪11%或更多。在1970年代,尽管失业率很高,通胀率却保持高位,恰恰是因为工人对通胀的预期已经提高到这个水平。经济学家决定把预期通胀作为一个决定通胀的独立因素,和失业率放到一起,以“增强”菲利普斯曲线。

Another complication comes from imports. Unemployment at home has little bearing on wages abroad. The price of anything consumers buy from the rest of the world will be determined by other forces. For this reason, some economists add a measure of import prices to the curve.
另一个把局面变复杂的因素是进口。国内的失业率对国外的工资水平没什么影响。消费者从世界其他地方购买的任何商品的价格由其他因素决定。为此,一些经济学家在菲利普斯曲线上增加了进口价格这个尺度。
Neither of these additions, however, can explain the missing inflation of recent years. Imports from countries like China may have depressed the price of some products, such as electrical appliances. But that is no reason why prices in general should be subdued. If China is holding down the price of one corner of the shopping basket, the central bank should be able to encourage other prices to rise to offset it. Inflation of 2% is perfectly compatible with some prices dropping steeply, as long as enough others rise sufficiently fast.
然而,两个新增的因素都无法解释近年通胀的消失。从中国等国家进口的产品可能压低了某些产品的价格,比如电器。但这不至于抑制总体价格。如果中国拉低了购物篮一角的价格,那么央行应该能够促使其他商品涨价以抵消其影响。只要有足够多的其他产品以足够快的速度涨价,那么2%的通胀率完全可以容许某些价格的暴跌。
Inflation expectations can also explain only part of the puzzle. They have been low for decades: in America, they have not exceeded 3% for 20 years, according to the Federal Reserve Bank of Cleveland. These subdued expectations have shifted the Phillips curve downwards, so that a given rate of unemployment is associated with a lower rate of inflation.
对通胀的预期也只能解释部分谜团。低预期已经持续了几十年:根据克利夫兰联邦储备银行的数据,在美国它们已经长达20年没有超过3%了。这种低预期已经让菲利普斯曲线向下偏移,让特定的失业率关联到更低的通胀率。
Middle of the riddle 迷雾之中 But what has happened to the curve in recent years is different: more akin to a rotation, rather than a shift up or down. Inflation has become seemingly insensitive to joblessness, yielding a curve that has become strangely flat. This may be because the unemployment rate misstates the amount of spare capacity or “slack” in the economy. By 2019 unemployment in America, Europe and Japan had fallen to surprisingly low levels, which tempted some people on the periphery of the labour force back into work. Japan’s firms found room to grow by hiring many women and old folk who had not been counted as unemployed.
但近年来这条曲线的走势很不一样:它更像是在水平旋转,而不是上下移动。通胀似乎对失业不敏感了,产生了一条异常扁平的曲线。这有可能是因为失业率没有准确反映经济中的剩余产能或称“闲置部分”。到2019年,美国、欧洲和日本的失业率已经跌至令人惊讶的低位,诱使一些蛰伏在劳动力队伍边缘地带的人群重回职场。日本企业通过雇用众多之前未被算作失业者的女性和老人找到了成长空间。
Inflation may also be slow to rise in a jobs boom for the same reason it is slow to fall in a bust. In downturns, firms are reluctant to lower wages, because of the harm to staff morale. But because they refrain from cutting wages in bad times, they may delay raising them in good. According to this view, wages will eventually pick up. It just takes time. And many other things, like a pandemic, can intervene before they do.
通胀率在就业热潮中爬升缓慢,可能还因为它在就业低迷期跌得慢。在低迷期,企业不大愿意减薪,因为怕损伤员工的士气。但因为它们在困难时期没有削减工资,在繁荣时期可能也会延迟涨工资。根据这种观点,工资最终是会上涨的。只是需要时间。而在它上涨之前,像疫情等许多其他事情都可能干扰其进程。
The impact of low unemployment would be easier to spot in the data if it were not so rare, according to Peter Hooper of Deutsche Bank, Frederic Mishkin of Columbia University and Amir Sufi of the University of Chicago in a paper published in 2019. To increase the number of observations, they unparcelled America into its separate states and cities. At this subnational level, they found numerous examples of red-hot jobs markets over the past few decades, and a clearer link to wage and price inflation. The local Phillips curve is “alive and well”, they note, and perhaps the national version is just “hibernating”.
德意志银行的彼得•霍珀(Peter Hooper)、哥伦比亚大学的弗雷德里克•米什金(Frederic Mishkin)和芝加哥大学的阿米尔•苏菲(Amir Sufi)在2019年发表的一篇论文中表示,如果数据不是那么稀缺的话,低失业率的影响会更容易被发现。为增加观测数,他们把整个美国拆分成州和城市来研究。在这种地方层级上,他们发现了过去几十年里就业市场火红的大量例子,而就业与工资和物价上涨的关联也更清晰地显现出来。他们指出,地方版菲利普斯曲线“很鲜活”,全国版可能只是在“冬眠”。
It may also take time for higher wages to translate into dearer prices. In bustling fruit-and-vegetable markets stalls display their prices in chalk, making them easy to scrub out and revise. But for many other firms, changing prices is costly. When inflation is low, they may change prices only infrequently: it does not seem worth printing a new menu just to change prices by 2%. This inertia, however, also means firms rarely have the opportunity to reprice their goods to reflect swings in their business. The economy has to move a lot before prices will move at all.
工资上涨转化为物价上涨可能也需要一段时间。在热闹的蔬果市场,摊贩们用粉笔写出价格,随时可以擦掉重写。但对许多其他公司来说,改价格花费不菲。通胀在低位时,它们可能只会偶尔地更改价格,因为看起来为把价格上调2%而重印菜单并不值得。但是,这种惯性也意味着企业很少有机会对产品重新定价以反映业务波动。经济需要发生很大的变化,物价才会开始动。
Although the flat Phillips curve puzzles central banks as much as anyone, they may be partly responsible for it. The curve is supposed to slope downwards (when inflation or unemployment is high, the other is low). But central banks’ policies tilt the other way. When inflation looks set to rise, they typically tighten their stance, generating a little more unemployment. When inflation is poised to fall, they do the opposite. The result is that unemployment edges up before inflation can, and goes down before inflation falls. Unemployment moves so that inflation will not.
尽管央行官员和所有其他人一样对平坦的菲利普斯曲线感到困惑,但他们可能对此负有部分责任。这条曲线本应向下倾斜(通胀率和失业率一个高时另一个低),但央行的政策却是另一种倾向。当通胀看起来必然要上升时,央行通常会收紧自己的货币政策,让失业略微增加。当通胀势必要下跌时,它们做相反的动作。其结果是,失业率抢在通胀之前上升或下降。失业率会变动以求通胀率不变。
The relationship between labour-market buoyancy and inflation still exists, according to this view. And central banks can still make some use of it. But precisely because they do, it does not appear in the data. “Who killed the Phillips curve?” asked Jim Bullard, an American central banker, at a conference of his peers in 2018. “The suspects are in this room.”
根据这种观点,劳动力市场的活跃程度和通胀之间的关联仍然存在。而央行仍然可以利用它。但正因如此,这种关系就不再显现在数据中。“谁杀死了菲利普斯曲线?”美联储官员吉姆•布拉德(Jim Bullard)在2018年的一次央行会议上问道,“嫌犯就在这个房间里。”
But what happens when the killers run out of ammunition? To keep the Phillips curve flat, central banks have to be able to cut interest rates whenever inflation threatens to fall. Yet they can run out of room to do so. They cannot lower interest rates much below zero, because people will take their money out of banks and hold onto cash instead.
但是,当杀手们的弹药用尽时会发生什么呢?为使菲利普斯曲线保持平坦,无论什么时候眼看通胀就要下行,央行都必须能够下调利率。但这种操作的空间可能会用尽。它们不能把利率降到低于零太多,因为这时人们会把钱从银行取出,转为持有现金。
When Mr Bullard spoke, the Federal Reserve expected the economy to continue strengthening, allowing it to keep raising interest rates. But that proved impossible. The Fed was able to raise interest rates no higher than 2.5% before it had to pause (in January 2019) then reverse course. The neutral interest rate proved to be lower than it thought. That left it little room to cut interest rates further when covid-19 struck.
布拉德说那句话时,美联储预期经济将继续走强,令其能够继续调高利率。结果证明这不可能。美联储只把利率调高到了不超过2.5%,就不得不在2019年1月刹车,然后掉头。事实证明中性利率比它预期的要低。这让它在新冠肺炎来袭时已经没有了进一步降息的空间。
The neutral interest rate has fallen, according to some observers, because of global capital flows. Heavy saving by the world’s ageing populations has resulted in too much money chasing too few investments. By lowering the neutral rate, this “global savings glut” has left central banks closer to the floor on interest rates than they would like. That has made it harder for them to offset any additional downward pressures on prices.
一些观察家认为,由于全球资本流动,中性利率已经下降。全世界不断老龄化的人口持有的巨额储蓄导致太多资金追逐太少的投资机会。这种“全球储蓄过剩”拉低了中性利率,使各国央行非己所愿地处于更靠近利率底部的位置。这让它们更难去抵销任何一点物价进一步下行的压力。
Friedman thought central banks could prevent inflation if sufficiently determined to do so. “There is no technical problem about how to end inflation,” he wrote in 1974. “The real obstacles are political.” Is reviving inflation any different? Central banks face two technical limits. First, they cannot lower interest rates much below zero. And they can only purchase financial assets, not consumer goods. Central banks can create unlimited amounts of money. But they cannot force anyone to spend it.
弗里德曼认为,只要有足够的决心,央行可以阻止通胀。他在1974年写道:“在如何结束通胀上不存在任何技术问题。真正的障碍是政治上的。”那么让通胀回升有何不同吗?央行面临两方面的技术限制。首先,它们无法把利率降到远低于零的水平。此外,它们只能购入金融资产而不能购买消费品。央行可以无限量地印钱,但不能强迫任何人花钱。

One solution is to work in tandem with the government, which can spend any money the central bank creates. Before covid-19, such dalliances were rare. But an increasing number of central banks, in both the rich and emerging world, are changing course. These partnerships will try to stop pandemic-related unemployment turning low inflation into outright deflation. If they fail it will be an economic disaster: mass joblessness coupled with negative inflation. And it will be no consolation to students of economics that this combination will remove the flatness from one of their discipline’s most famous curves.
一种解决方案是与政府合作,这可以把央行印出来的钱都花掉。在新冠疫情之前这类联手很少见。但是,无论是在富裕世界还是新兴国家,越来越多央行都在改变路线。这些合作将努力阻止疫情引发的失业把低通胀变成完全的通缩。如果它们失败了,那将是一场经济灾难:大规模失业伴随负通胀。这种组合将让经济学最著名的一条曲线不再平坦,却不会给这个专业的学生带去多少安慰。