美國股市奇特的九月效應

As they turn the calendar to September, investors have good reason to be wary.
日子行進到九月，投資者有必要警惕起來了。

The docket is full of news that could disrupt the Standard & Poor's 500's roughly 7% climb since June. On Friday, the Labor Department releases the latest jobs figures. On Sept. 12, a German court rules on the constitutionality of a critical rescue fund for the euro zone. And the Federal Reserve is expected soon to make clear whether there will be a third round of 'quantitative easing.'
從日程表上的重要事件來看，標準普爾500指數自六月以來大約7%的升幅隨時可能玩完。8月31日，美國勞工部(Labor Department)公佈了最新的就業數據。9月12日，德國某法院將就歐元區一個關鍵的救助基金計劃是否符合憲法規定作出裁決。此外，美聯儲(Federal Reserve)估計很快也將就是否推出第三輪“量化寬鬆”政策作出明確表態。

But of special interest to historians is the calendar itself. Put simply, Sept. 1 marks the start of a historically miserable Month for stocks.
但在史學家的眼裏，日程表本身最有意思。因爲歷史經驗表明，一旦日曆翻到9月1日，對美國股市來說就意味着悲慘的一個月開始了。

That isn't reason enough for investors to make any drastic moves with their portfolios. But they could profit by avoiding stocks that have suffered pullbacks, say some analysts.
這當然不足以促使投資者對自己的投資組合作出任何重大調整。但有分析師表示，投資者如果能夠規避那些歷來習慣在九月下跌的股票，就可能獲利。

Since 1926, in any given month, stocks of large companies have risen 0.9% on average, according to Bank of America Merrill Lynch. But in September, they have fallen by 0.8%, the only month with a negative average return.
據美銀美林(Bank of America Merrill Lynch)統計，自1926年以來的任意月份，大盤股平均上漲0.9%，但唯有九月其平均表現是下跌的，這個月大盤股平均下跌0.8%。

'For whatever reason, there's a predictable pattern where September has bad performance,' says Steven DeSanctis a strategist with Bank of America Merrill Lynch's equity research team.
美銀美林股票研究團隊的策略師史蒂文・德森提斯(Steven DeSanctis)表示，不論出於何種原因，九月美股表現差已經有定式可循。

The trend has baffled researchers for decades. Striking September events, such as the 2008 collapse of Lehman Bros. and the 2001 terrorist attacks, are partly responsible for the bad average, but they can't explain the problems entirely.
這種定式已經困擾了研究人員數十年。一些“碰巧”發生在九月份的大事件，例如2008年的雷曼兄弟(Lehman Bros)倒閉、2001年的恐怖襲擊，與股市在九月份糟糕的平均表現不無關係，但即便如此，也無法完整地解釋這個現象。

For example, stocks have risen in only 50% of Septembers since 1926, the worst of any month and far below the 61.8% average success rate.
例如，自1926年以來的所有九月中，只有50%的情況是股市上漲的，比其他任何月份的統計結果都要差，遠低於61.8%的平均上漲機率。

If someone started investing in 1802 and kept his money in stocks only during September, he would have lost more than half of his money by 2006, according to researchers at the University of Kansas. Do the same during any other month, and he would have gained at least 79% during the period.
堪薩斯大學(University of Kansas)的研究人員發現，如果某位投資者從1802年進入股市，而且只在九月進行投資，那麼到2006年他會虧掉一半以上的資金。而在同樣的時間和條件下，如果換作其他任何一個月份，這位投資者的賬面價值至少會上漲79%。

Explanations for the September swoon are hard to come by, and harder to swallow.
美國股市的九月厄運讓人很難琢磨，而且至今也沒有一個令人信服的解釋。

The University of Kansas study suggests a sharp drop-off in the amount of daylight in New York in September might trigger seasonal affective disorder and make some traders more risk-averse. On average, New Yorkers see 3,147 fewer minutes of daylight in September than they do in August, the biggest drop of any month, according to the study.
堪薩斯大學的研究推測，九月份紐約白晝時間的大幅驟減可能引發了季節性的情緒紊亂，導致一些交易員的避險情緒加重。此項研究發現，在紐約，九月的白晝比八月平均減少3147分鐘，減幅爲各月之最。

But even the researchers aren't confident in that explanation. 'From the best of my ability, I think there's something up with September. No matter how you slice it up, it's bad,' says the University of Kansas' Mark Haug, one of the authors of the report. 'It's frustrating to not have an explanation.'
但即便研究人員自己對這個解釋也不太確定。該研究論文的聯名作者、堪薩斯大學的馬克・豪格(Mark Haug)說，“我最多隻能說，九月份確實有些不同尋常的事發生。不管是什麼，都很糟糕。但找不到一個合理的解釋讓人很抓狂。”

To be sure, September's poor performance could be due to mere chance. 'I always look at this stuff and wonder, 'Is it randomness?'' says Sam Stovall, chief equity strategist with S&P Capital IQ.
當然，九月股市表現糟糕也可能完全屬於偶然事件。標普資本智商公司(S&P Capital IQ)首席股票策略師山姆・斯托瓦爾(Sam Stovall)表示，“我每每想到這件事，就忍不住納悶，‘這會不會就是隨機性的呢？’”

Mr. Stovall's theory: poor earnings guidance for the third quarter and the rest of the calendar year causes weary investors to sell shares.
斯托瓦爾的解釋是：公司欠佳的第三季度及當年後續時間盈利預測促使謹慎的投資者拋出股票。Another possibility posed by researchers: tax-loss harvesting. A 1986 law forced most mutual funds to move the end of their tax years to October. So, many portfolio managers might be selling stocks with recent losses in September and October to take advantage of tax breaks, says Scott Gibson, a finance professor at the College of William and Mary who has studied the phenomenon.
研究人員提出的另一個猜想是：稅收虧損收割(tax-loss harvesting)。根據1986年制定的一項法律，大多數共同基金的稅收年度必須在10月份截止。威廉瑪麗學院(College of William and Mary)的金融學教授斯科特・吉布森(Scott Gibson)對此現象也進行了研究，他表示，因爲這個規定，很多投資組合基金經理可能會在九月和十月賣掉最近有浮動虧損的股票，以獲得減免稅的好處。

In 1990, when the rules took full effect, stocks with recent losses that were widely held by mutual funds lagged their benchmarks by almost 7 percentage points in October. Those same stocks beat their benchmarks by nearly 7 points in November, as the effect wore off, Prof. Gibson says.
吉布森教授指出，1990年，上述法規完全生效時，共同基金普遍持有的最近浮虧的股票在十月份跑輸對應的基準指數近七個百分點。而到了十一月，稅收效應消失後，同樣一撥股票又跑贏基準指數近七個百分點。

Since then, the effect has become less pronounced, presumably as more mutual funds caught on.
此後，稅收效應的影響變得不再那麼明顯，這或許是因爲有更多共同基金參與了進來。

But Prof. Gibson says it is strong enough that investors looking to pick up shares on the cheap would be well-served to wait. Companies that have more than 5% of their shares held by funds and have seen recent losses are candidates for continued drops in September and October, he says.
但吉布森教授表示，稅收效應的影響還是很大的，希望抄底的投資者應當耐心等待。他說，基金持股比例超過5%且近期有浮虧的上市公司，其股價最可能在九月和十月繼續下跌。

That would disqualify computer-seller Dell, which has dropped 10.8% in the last three months and is about 32% owned by mutual funds.
電腦銷售公司戴爾(Dell)似乎很符合這個標準，該股過去三個月下跌了10.8%，其共同基金的持股比例高達32%左右。

Other companies with poor recent performance and high fund ownership include Delta, Ford, Hewlett-Packard,Netflix, and Research In Motion.
其他近期股價走弱且基金持股比例較高的上市公司包括達美航空(Delta)、福特汽車(Ford)、惠普(Hewlett-Packard)、Netflix和Research In Motion等。

But with rational explanations hard to come by, investors should stop short of making big moves out of equities, Mr. Stovall says.
但斯托瓦爾指出，對於美股的九月厄運，由於很難找到合理的解釋，投資者也不應大舉做空股票。

'You're better off treating this information the way you would the pilot coming over the loudspeakers and saying 'Please fasten your safety belt,'' Mr. Stovall says. 'He's not saying 'Don the parachutes and assemble by the door.''
斯托瓦爾說，對於這個九月效應和分析人士的提醒，投資者最好就像在坐飛機時對待機長通過麥克風的喊話一樣，“繫好安全帶”就行了，而不應將機長的喊話理解爲“背上降落傘包，到機艙門口集合”。