市場比經濟學家更擅長預測衰退

Although economics was derided by the historian Thomas Carlyle as the “dismal science,” it is optimism that infects the profession — and it runs so deep that economists rarely see recessions coming.

雖然歷史學家托馬斯•卡萊爾(Thomas Carlyle)曾把經濟學揶揄爲“沉悶的科學”，但實際上這一學科的問題在於受到樂觀情緒的感染，這種影響如此之深，以至於很少有經濟學家能預見經濟衰退的到來。

Even in early 2008, when markets were crashing, a survey of leading forecasters by the Philadelphia branch of the Federal Reserve showed that none predicted negative growth for the US that year.

即便在2008年初市場開始崩盤之際，費城聯邦儲備銀行(Philadelphia Fed)對多位著名預測專家所做的一項調查顯示，沒有一個人預測當年美國經濟會出現負增長。

Now, despite evidence that the world economy is near to another recession, a similar survey shows that not one of the 40 leading economists believes there will be a US downturn this year.

如今，儘管有證據表明世界經濟正在滑向新一輪衰退，但一項類似的調查顯示，在受訪的40位著名經濟學家中，沒有一人認爲美國經濟今年將陷入低迷。

Clearly, economists are not listening to the markets, which are more worried. In 1966, the Nobel-winning economist Paul Samuelson quipped that the stock market had “predicted nine out of the last five recessions,” and writers still quote him to disparage the predictive power of markets.

顯然，經濟學家們沒有傾聽市場的信號——市場更加擔憂。1966年，諾貝爾經濟學獎得主保羅•薩繆爾森(Paul Samuelson)曾開玩笑說：股市曾“預言了過去5次經濟衰退中的9次”，而經濟學家寫文章時仍會引用他的話來貶低市場的預測能力。

Samuelson, though, was no more impressed by his fellow economists. The analysis company Ned Davis Research has shown that “economists, as a consensus, called exactly none” of the last seven recessions, dating back to 1970.

然而，薩繆爾森對經濟學家同行的評價也不高。分析公司Ned Davis Research的研究表明，對於可追溯至1970年的7次經濟衰退，經濟學家（就共識而言）實際上一次都未預測出來。

To see how well markets anticipate trouble for the economy, I looked at data for the past 50 years for periods when Wall Street’s Standard Poor’s 500 index fell from its most recent peak by 10, 15 or 20 per cent. It turned out that the market declined by at least 15 per cent from its peak typically six months before the seven US recessions. In short, the market has a habit of sniffing out trouble in a timely manner.

爲了弄清楚市場在多大程度上能預測經濟危機，我梳理了過去50年華爾街的標準普爾500指數(SP 500)從最新的峯值跌去10%、15%或20%後各個時期的數據。結果，在美國經濟7次出現衰退的六個月前，股市通常都會從最高點下跌至少15%。簡言之，股市擁有及時嗅出危機來臨的能力。

As Samuelson suggested, it is true that the stock market also sends false signals. The SP 500 has suffered 15 per cent declines 12 times since 1965, so there were five times when a sharp decline was not followed by a recession, most recentlyin 2011.

正如薩繆爾森所提出的，股市也會發出虛假信號。自1965年以來，標普500指數跌幅達15%的次數爲12次，所以，股指大幅下跌後沒有出現衰退的次數爲5次——最近一次是在2011年。

All told, however, a sharp decline in the SP 500 has signalled a recession nearly 60 per cent of the time. By contrast, the consensus view of economists has an accuracy rate of zero per cent.

然而，總的來說，標普500指數大幅下跌在近60%的情況下預示着衰退。相比之下，經濟學家共識的準確率爲零。

Twice this year, the SP has approached the 1,800 level, which would represent a 15 per cent decline, then recovered. If it falls below that mark, it would suggest a probability of nearly 60 per cent that the US economy is in or is entering a recession.

今年以來，標普指數已經兩次跌至接近1800點水平——跌至1800點將代表跌幅達15%——但隨後又止跌回升。如果標普指數跌至這一水平之下，那將暗示，美國經濟已陷入或正在走向衰退的概率爲近60%。

The global picture is similar. Because there are always fast-growing nations somewhere, the global economy rarely shrinks as a whole. Typically, global recessions begin when growth falls below 2 per cent, which has happened five times in the past 50 years — and the markets anticipated each one.

全球的情況與此相似。因爲總有某些國家快速增長，所以全球經濟作爲一個整體極少萎縮。通常情況下，全球經濟衰退在增長低於2%的時候開始，過去50年裏這種情況發生過五次——每次都被市場預測到。

I looked at the MSCI World Index to 1970, when its records began. The market fell by at least a fifth from its recent peak eight times; before all five global recessions and on three other occasions. That would infer 63 per cent accuracy.

我檢索了自1970年開始有記錄的摩根士丹利資本國際世界指數(MSCI World index)。該指數從最高點下跌至少20%的次數爲8次；在所有5次全球衰退出現前都曾這樣大幅下跌。這意味着該指數預測衰退的準確率爲63%。

From its peak last year, the MSCI World Index reached a maximum decline of 19 per cent on February 11, then recovered.

自去年達到峯值以來，摩根士丹利資本國際世界指數在今年2月11日觸及19%的最大跌幅，隨後反彈。

If the index drops again and breaches the 20 per cent threshold soon, the message will be clear: there is a better than even chance of a global recession this year.

如果該指數不久再次下跌且跌破20%的閾值，那將傳遞出明確的信息：今年全球經濟出現衰退的可能性將超過50%。

There are no certainties but the collective wisdom of markets has proven more reliable than the thinking of economists.

這方面沒有確定性可言，但市場的“集體智慧”已被證明比經濟學家的思考更可靠。

With real money at risk, investors seem to be highly alert to signs of imminent recessions, while economists seem to be motivated by a fear of bucking the professional consensus. Their models are not built to capture dramatic shifts and their forecasts tend to move in tiny steps.

由於要承擔真切的資金風險，投資者似乎對預示經濟衰退即將到來的跡象高度警覺，而經濟學家們似乎出於害怕顛覆業內共識而畏首畏尾。他們建立的模型不是爲了捕捉戲劇性的突變，而他們對預測的調整往往幅度很小。

They rarely risk a sharp move into negative territory. The cheerful science would probably do better by listening to the markets.

他們很少冒險大幅調整至負值區域。這門“樂觀的科學”如果能聆聽市場的信號，或許會有更好表現。