隱藏的圖表--為什麼低失業率不再能抬高通膨？

 Hidden figures 隱藏的圖表

Why does low unemployment no longer lift inflation? 為什麼低失業率不再能抬高通膨？

The Phillips curve, the logic of which guides central banks today, has become oddly flat 菲利普曲線，現今央行依循的邏輯指南，變得出奇平坦

Aug 22nd 2020

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10時左右，印尼戰俘營的燈光會神祕地變暗，令日本守衛困惑。他們未發現那些權充浸沒式加熱器的玩意。那是紐西蘭囚犯菲利普（William Phillips）巧手拼湊而成，用來泡茶給獄友喝。這些祕密的發明只是他足智多謀的一例。

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.

第二次世界大戰後，他建立了一個經濟所得迴圈流動的「液壓」模型--由水箱、閥門和管子組成的迷宮，這使他贏得倫敦經濟學院的聘任。但是，這兩項功績都不是當今經濟學家無人不知菲利普大名的原因。他的名氣立足於1958年發表的「快速而骯髒的」研究，記錄英國工資通膨與失業之間長達數十年的驚人關係：當一方偏低，另一方就走高。他大致用手繪出一條向下傾斜的曲線，闡述這一點。這就是後來聞名於世的菲利普斯曲線，被描述成「可能是最重要的一種總體經濟關係」，也被稱為他所做過的「最不紮實的研究」。

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.

菲利普斯曲線的可靠性和形狀，過去60年來不只一次受質疑，包括2007-09年的全球金融危機期間。但是曲線的邏輯仍然指導著今天的央行。

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.

當商業興隆且失業率低下時，央行官員擔心，勞工要求的加薪幅度將高於通膨率，以及他們生產力的增幅。如果企業藉提高價格將調高的工資轉嫁客戶，通膨率將上升。如果央行希望避免這種情況，他們將提高貸款利率，減緩經濟擴張，並抑制工資壓力。

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.

相反的情況發生在曲線的另一端。失業率高使工資和支出趨於扁平，造成通膨下降壓力。為抵銷此現象，決策者通常會調降利率。

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.

央行官員希望在兩者之間找到立足點：通膨率位於他們想要的水平，而失業率不至於高到、或低到使通膨率偏離那個水平。在樂觀情況下，他們的目標是設定一個「中性」利率，使通膨率保持不變。

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.

大多數富國央行把目標通膨率訂在2％上下。在這種溫和的水平，通膨不會使財務計劃大幅地複雜化，或削弱對貨幣的信心。但這允許工資相對於物價適度下降，卻沒有人會為荷包消瘦所苦，勞動力變便宜，到頭來可能有助於在景氣低迷時保住工作。

In recent years, however, inflation has fallen persistently short of the central bank’s target in many countries. 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.

但是近年來，許多國家的通膨率一直低於央行目標。全球金融危機爆發後，如此低的通膨不足為奇。失業率急劇上升，美國在2009年10月達到10％。在這種情況下，唯一令人訝異的是通膨率沒有降得更低。然而，經濟復甦之後，通膨率持續文風不動，即使美國、歐元區和日本的失業率降幅大得異常。這迫使經濟學家重新思考兩者關係。

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.

1960年代一些懷疑論者（其中最受關注的或許是傅利曼）指出，失業率與通膨率之間的關係，就像背後的預期一樣牢靠。如果通膨率預計為2％，勞工可能因失業率低而放膽要求加薪3%或4％。但若預計通膨率為10％，勞工同樣可能有恃無恐地要求加薪11％或更多。在1970年代，儘管失業率很高，通膨率持續居高不下，正是因為勞工對通膨的預期大幅提高。經濟學家決定「擴充」菲利普曲線，加入通膨預期，與失業率並列為決定通膨的獨立因素。

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.

另一個複雜因素來自進口。國內的失業對海外的工資影響微乎其微。消費者從世界各地買來的任何產品的價格，取決於其他力量。因此，一些經濟學家把進口物價指標也加入曲線。

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，添加了這些，還是不能解釋為何近年來通膨消失無蹤。從中國大陸等國進口產品，可能壓低了某些產品的價格，例如家用電器。但這絕不是整體物價遭壓抑的原因。如果中國大陸壓低購物籃一角的物價，央行應有能力鼓勵其他價格上漲，予以抵消。2％的通膨率絕對可以包容某些物價陡降，只要夠多的其他產品漲幅夠大即可。

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.

通膨預期也只能解釋一部分謎團。它們已經低迷幾十年：美國已經20年沒有超過3％，根據克利夫蘭聯邦準備銀行數據。這些低迷的預期使菲利普曲線向下移動，因此特定的失業率與較低的通貨膨脹率產生關聯。

Middle of the riddle 謎霧之中

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.

但是，近年來曲線發生不同的變化：比起向上或向下移動，更像是旋轉。通膨似乎對失業不敏感，產生的曲線變得異常平坦。這可能是因為失業率錯誤陳述閒置產能的量，或經濟「疲軟」的程度。到2019年，美國、歐洲和日本的失業率已降到令人驚訝的低水平，這吸引部分處於勞動力邊緣的人重返就業市場。日本公司找到了成長空間，僱用許多未被算成失業者的婦女和老人。

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.

通膨在就業市場繁榮時也可能緩慢上升，跟不景氣時緩慢下降的原因相同。在低迷時期，公司不願降低工資，因為這有損員工士氣。但是，正因他們避免在艱困時期削減工資，繁榮時期可能延遲提高工資。根據這種觀點，工資終將回升，只是需要時間。還有許多其他因素，例如大流行病，也可能是工資上揚前的干預因素。

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”.

低失業率的影響若不是那麼罕見，否則本應更容易在數據中發現，德意志銀行的霍珀（Peter Hooper）、哥倫比亞大學的米什金（Frederic Mishkin）和芝加哥大學的蘇菲（Amir Sufi）在2019年發表的論文中這麼說。為提高觀察點，他們將美國分拆成個別的州和城市。在國家以下的層級，他們發現過去幾十年眾多就業市場火熱的例證，工資和物價上漲的關聯也更清晰了。他們指出，各地的菲利普曲線仍然「生氣蓬勃」，也許全國版曲線只是在「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.

工資上漲也可能需要一些時間，才能轉化為物價上漲。在交易繁忙的果菜市場，攤販用粉筆標示價格，很容易擦掉修改。但是對其他許多公司來說，調整價格要付出昂貴代價。通膨低迷時，可能偶爾才調整售價：只為漲價2％而重印菜單，似乎不值得。不過，這種惰性也意味公司很少有機會對產品重新定價，以反映市況起伏。經濟必須歷經重大變化，價格才會有所變動。

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.

儘管平坦的菲利普曲線，使央行和其他人一樣困惑，但他們可能得負部分責任。該曲線照理說應該向下傾斜（當通膨率或失業率在高點時，另一個則在低點）。但是央行政策總向另一邊傾斜。當通膨看起來會上升時，他們通常會緊縮立場，引發更多的失業。當通膨率準備下降時，他們就反其道而行。結果造成失業率在通膨上升之前先上升，在通膨下降之前下降。結果失業率變動，但通膨率不動。

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.”

根據這種觀點，勞動市場起伏與通膨之間的關係仍然存在，央行仍然可以稍加運用。但正因他們這麼做，數據才反映不出來。 「誰殺了菲利普曲線？」美國央行官員布拉德（Jim Bullard）在2018年與同事開會時問道。「嫌疑犯就在這個房間裡。」

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，一旦殺手的彈藥耗盡，會發生何事？為了使菲利普曲線保持平坦，央行一察覺通膨有下降之虞，就必須降低利率。但他們可能沒有餘裕這麼做了：不能把利率降到遠低於零，因為這會促使人們從銀行提款，寧可抱持現金。

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.

布拉德發言當時，聯準會（Fed）還預期經濟仍將走強，可持續提高利率。但事後證明這是不可能的。Fed只把利率升到2.5%，就必須暫停升息（在2019年1月），然後更改弦易轍。中性利率證明比Fed預期來得低。新冠病毒來襲時，Fed進一步降息的空間寥寥無幾。

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.

一些觀察家認為，由於全球資本流動，中性利率已經下降。全球高齡化人口大量儲蓄，導致太多的資金追逐太少的投資標的。這種「全球儲蓄過剩」使中性利率下降，造成各國央行比預期更接近利率下限。這使他們更難抵消物價進一步走低壓力。

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.

傅利曼認為，央行如果下足決心，可以防止通膨。他在1974年寫道：「終結通貨膨脹沒有技術上的問題。真正的障礙是政治上的。」通膨復熾有什麼不同？央行面臨兩個技術限制。首先，他們不能將利率降到遠低於零。其次，他們只能買金融資產，不能買消費品。央行可以印製無限量的錢幣，卻不能強迫任何人花錢。

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. ■

一種解決方法是與政府協力合作，央行印多少鈔票，政府就可花掉多少。在新冠肺炎疫情前，這種眉來眼去很少見。但是，愈來愈多的央行都在改變路線，富國和新興國家皆然。有了這些夥伴關係，可試著阻止疫情相關失業把低通膨變成徹底的通縮。如果失敗，那將是場經濟災難：大規模失業和通縮。這種結合將移除經濟學著名曲線的平坦性，但對研究經濟學的人毫無慰藉可言。 ■