????本周股市大幅跳水，華爾街的經(jīng)濟學(xué)家們爭先恐后地重新調(diào)整經(jīng)濟再度陷入衰退的預(yù)測。短短幾天之內(nèi)，一個共識浮出水面：大多數(shù)的分析師認(rèn)為經(jīng)濟二次探底的可能性在30%-40%之間。

????高盛（Goldman Sachs）首席經(jīng)濟學(xué)家最近表示在接下來的9個月經(jīng)濟再次陷入衰退的可能性達(dá)到三分之一。標(biāo)普（Standard & Poor's）的經(jīng)濟學(xué)家（這些經(jīng)濟學(xué)家獨立于評級部門）以及美銀美林（Bank of America Merrill Lynch）的經(jīng)濟學(xué)家們都將可能性提高到了35%。德意志銀行（Deutsche Bank）則定得更高，他們的預(yù)測值敲定為40%。

????資產(chǎn)管理巨頭貝萊德（BlackRock）的首席證劵策略師鮑勃?多爾上周三表示，該公司認(rèn)為經(jīng)濟再次出現(xiàn)衰退的可能性為30%。他寫道，“我們預(yù)計經(jīng)濟不會出現(xiàn)強勁的增長周期，但也不會出現(xiàn)再度衰退。”

????考慮到現(xiàn)在市場的狂熱，這樣的預(yù)測雖然遠(yuǎn)談不上樂觀，但還是令人寬慰的：這些策略分析師都認(rèn)為經(jīng)濟不太可能出現(xiàn)二次探底。諸位高人紛紛發(fā)表預(yù)測自己，我們最好別忘了，上一次經(jīng)濟衰退時，他們的預(yù)測就落空過。

????根據(jù)美國國家經(jīng)濟研究局（National Bureau of Economic Research）的記錄，上次經(jīng)濟衰退從2007年12月正式開始。2008年1月，彭博社（Bloomberg）調(diào)查的經(jīng)濟學(xué)家認(rèn)為經(jīng)濟衰退的可能性為40%。同年2月，經(jīng)濟學(xué)家們將可能性提高到了50%，此后一直維持在該水平【4月在投資銀行與證券交易公司貝爾斯登（Bear Stearns）倒閉時出現(xiàn)過短暫上升】。9月初，就在雷曼兄弟（Lehman Brothers）倒閉和股市開始暴跌的前幾天，經(jīng)濟學(xué)家仍然將經(jīng)濟衰退的可能性定為51%。

????隨大流

????這些幾率的驚人之處在于它們變化的頻率之快。當(dāng)年10月，經(jīng)濟學(xué)家宣稱經(jīng)濟衰退即將到來的幾率高達(dá)90%（當(dāng)時除了穴居原始人，應(yīng)該沒人不知道經(jīng)濟將陷入衰退了吧。）

????最近一次預(yù)測調(diào)整也同樣極其突然。今年6月，預(yù)測者認(rèn)為出現(xiàn)衰退的可能性只有15%；到7月，可能性降至13.8%。隨著越來越多的經(jīng)濟學(xué)家（不可思議的類似）給出30%-40%的預(yù)測范圍，8月份的調(diào)查數(shù)據(jù)將會有顯著提高。

????2008年和眼下的情形類似，經(jīng)濟學(xué)家修正預(yù)測的方式都是應(yīng)激式的。兩者都發(fā)生在股市強烈震蕩之后。每一次市場都讓分析人士出乎意料，分析師隨后再根據(jù)市場下滑調(diào)整預(yù)期。

????這是不是意味著市場在左右分析師的預(yù)測？不是狗搖尾巴，而是尾巴搖狗？這些調(diào)整本身是合情合理的，因為市場崩盤會摧毀上萬億美元的公司及個人財富，放大可能誘發(fā)衰退的因素。

????賴斯大學(xué)（Rice University）商學(xué)院教授古斯塔沃?古隆說：“許多衰退共有的問題是它們都是由意料之外的事件引發(fā)的”。古隆指出70年代的石油危機和08年的金融危機出乎許多預(yù)測者的意料。他說：“經(jīng)濟學(xué)家失手是因為這類事件大都難以預(yù)測。”

????但是分析師在股市大跌之后做出調(diào)整的幅度和速度讓預(yù)測這項行為本身變得十分可疑。經(jīng)濟學(xué)家對市場反應(yīng)強烈，不過多爾指出，自大蕭條以來，跌幅達(dá)15%或以上的股市下跌共計有30次，但只有兩次股災(zāi)引起了衰退。

????事實上，導(dǎo)致近期股市暴跌的事件有很多，包括美國債務(wù)評級遭到下調(diào)，華盛頓的債務(wù)上限談判僵局以及歐洲的主權(quán)債務(wù)危機，這些都已經(jīng)持續(xù)了數(shù)月。經(jīng)濟指標(biāo)也令人擔(dān)憂。今年夏季美國的招聘和消費支出指數(shù)雙雙下跌。制造業(yè)活動也同樣衰弱。國內(nèi)生產(chǎn)總值（GDP）增長雖不是負(fù)數(shù)——一般認(rèn)為連續(xù)兩個季度GDP負(fù)增長則意味著經(jīng)濟衰退——但也只有低得可憐的1.3%。

????與此同時，債券投資者大量買入美國國債，遠(yuǎn)離風(fēng)險高的投機性債券。法國巴黎投資（BNP Paribas Investment Partners）全球信貸分析師馬丁?福里得森認(rèn)為，垃圾債券利差現(xiàn)在顯示經(jīng)濟陷入衰退的幾率為48%。福里得森補充表示，現(xiàn)在的利差表明高收益的債券跌幅過大。

????絕大多數(shù)預(yù)測者仍然認(rèn)為二次衰退不太可能。貝萊德的多爾寫道，首次申請失業(yè)金人數(shù)不斷減少時出現(xiàn)經(jīng)濟衰退的情況十分罕見。他將現(xiàn)在的情況與08年做了比較，當(dāng)時連黃金的價格都在下跌，這說明當(dāng)時存在債務(wù)通縮問題。他說，現(xiàn)在金價上漲說明投資者期待著新的經(jīng)濟刺激方案。多爾建議投資者把現(xiàn)金投到市場中去。

????有些經(jīng)濟學(xué)家對此持有不同意見。格魯斯基-謝菲資產(chǎn)管理公司（Gluskin Sheff）的大衛(wèi)?羅森博格就是其中之一。這位資深市場分析家在2008年1月曾指出經(jīng)濟已經(jīng)處于衰退。他最近的言論嘲笑了所謂的共識。他撰文說，“懷孕還是沒懷孕，這是非此即彼的事，是否陷入經(jīng)濟衰退也是如此。”

????羅森博格在6月接受《財富》雜志（Fortune）訪問時還說“債券市場也顯示衰退即將來臨”，他認(rèn)為出現(xiàn)二次探底的可能性為99%。他說：“華爾街不要再說35%的可能性這種廢話了。”

????As stocks took a blistering dive this week, Wall Street economists scrambled to readjust their forecasts of the likelihood that the economy is headed for another recession. In a matter of days, a consensus quickly emerged: Most strategists now place the odds of a double dip at 30-40%.

????Goldman Sachs' (GS) chief economist recently announced that there was a one-in-three chance that there will be another recession in the next nine months. The economists at both Standard & Poor's (who work separately from the ratings division) and Bank of America Merrill Lynch (BAC) moved their recession meters to 35%. Deutsche Bank (DB) aimed a little higher, placing its estimate at 40%.

????Bob Doll, the chief equities strategist at BlackRock (BLK), announced Wednesday that the asset management giant sees a 30% chance of a recession. "We don't anticipate a vigorous economic cycle, but we are not arguing for recession either," he wrote.

????Given the current mania in the markets, such prognostications, while far from cheery, are still comforting: The strategists agree that the economy probably won't double dip. But as the oddsmakers weigh in, it's important to remember that they didn't exactly hit the ball out of the park the last time around.

????The last recession officially started in December of 2007, according to the National Bureau of Economic Research. In January of 2008, economists surveyed by Bloomberg put the likelihood of a recession at 40%. That February, they lifted the odds to 50%--and then left them there for months (there was a brief spike in April, after Bear Stearns went under). In early September, just days before Lehman Brothers collapsed and the stock market imploded, economists still placed the probability of a recession at just 51%.

????Reacting with the pack

????What's incredible about those odds is the speed at which they changed. That October, economists declared a 90% chance that a recession was coming (by then, you'd have to be a cave-dweller to think otherwise).

????The latest revisions are similarly drastic. This June, forecasters saw a mere 15% chance of a recession; in July, that number actually dipped to 13.8%. As more and more economists roll out their (uncannily similar) estimates in the 30-40% range, it seems likely that August's survey will show a marked increase.

????In both 2008 and today, economists modified their estimates in a reactionary fashion: Both revisions occurred after the stock market had already tanked. In each case, the market caught strategists by surprise, and strategists adjusted their forecasts in response to the dips.

????Does that mean the tail, i.e. the market, is wagging the dog? The revisions themselves are justified; market crashes, which can destroy trillions of dollars in corporate and personal wealth, can amplify recessionary factors.

????"One of the problems with many recessions is that they're triggered by unexpected events," says Gustavo Grullon, a professor at Rice University's school of business. Grullon points out that the oil crisis in the 1970's and the financial crisis in 2008 caught many forecasters by surprise. "Economists are having trouble because most of those events are really unpredictable," he says.

????But the magnitude -- and velocity -- at which strategists adjust their estimates after stocks crash renders the practice of oddsmaking suspect. Economists react strongly to the market -- but Doll pointed out that there have been 30 market declines of 15% or more since the Great Depression, and that only two led to recessions.

????Indeed, many of the events that precipitated the latest crash -- the downgrading of U.S. debt, the political gridlock in Washington, and the European sovereign debt crisis -- have been unfolding for months. Economic indicators have also been dreadful. Hiring and consumer spending both took a dip this summer. So did manufacturing activity. GDP growth hasn't turned negative -- the rule of thumb is that two quarters of negative growth signify a recession -- but the economy grew last quarter at a paltry 1.3%.

????Bond investors, meanwhile, have piled into Treasuries and fled speculative debt. Junk bond spreads now signal a 48% chance of a recession, according to Martin Fridson, global credit strategist at BNP Paribas Investment Partners. Fridson went on to add that the spread meant that high yield bonds had probably fallen too much.

????Most forecasters still maintain that a second recession is unlikely. BlackRock's Doll wrote that it would be rare for a recession to begin while initial unemployment claims were declining. He contrasted the current environment with the situation in 2008, when even the price of gold was declining, signifying a "deflationary debt problem." The rise in gold prices today, he said, indicates that investors expect another stimulus. Doll advised investors to put their cash to work in the market.

????Not all economists agree. One strategist who has veered from the pack is Gluskin Sheff's David Rosenberg, the market Cassandra who said in January of 2008 that the economy was already in a recession. In a recent note, Rosenberg mocked the new consensus. "You cannot be sort of pregnant any more than you can maybe, perhaps, be in a recessionary state," he wrote.

????"The bond market also clearly has recession in its sights," added Rosenberg, who told Fortune in June that there was a 99% chance of a double dip. "None of this namby pamby '35% odds' stuff out of Wall Street."