【英语生活】抄底的时机到了吗？(上)

As world stock markets plunged last month, investors were able to take heart from the latest words of Warren Buffett: he announced he was buying stocks. "A simple rule dictates my buying: be fearful when others are greedy, and be greedy when others are fearful," proclaimed the man known as the Sage of Omaha. "And most certainly, fear is now widespread, gripping even seasoned investors."Nobody could disagree. But the extreme fear that was in evidence did not guarantee that stocks had hit a bottom. Mr Buffett acknowledged as much in his column for The New York Times and advised investors not even to try to time the market. His point was that stocks were cheap, so people should not take the risk of waiting.

"I haven't the faintest idea as to whether stocks will be higher or lower a month - or a year - from now," he wrote. "What is likely, however, is that the market will move higher, perhaps substantially so, well before either sentiment or the economy turns up. So if you wait for the robins, spring will be over."

But is there a way of telling when equities might have hit bottom? Certainly, when fear overcomes greed to this extent, attempts to assess a stock's value according to fundamental measures go out of the window. Instead, all people have to go on is history. Yet precedents as extreme as last month's "Black October" are few. Only four periods in the past 100 years (two of them during the 1930s) match the 46 per cent slide since the Standard & Poor's 500, the world's most widely tracked index, reached an all-time high in October last year.

In the weeks since its latest extreme sell-off, the S&P regained as much as 20 per cent at one point but continues to trade in a volatile range. Almost all other markets worldwide have displayed similar patterns, shedding even more than the US and rebounding more before lapsing into a range.

Nobody thinks that anything like normality has been restored; the weeks since then have included the biggest crash in hist-ory for the foreign ex-change market and further acute difficulties for the credit market. Historical pointers look ominous too: after the crash of 1929, anybody buying when the market started to stabilise would have lost more than three-quarters of their money over the next two years.

But some are beginning to set aside such fears. "For an unparalleled 20 years, global equities, especially US equities, have been overpriced," Jeremy Grantham, founder of the Grantham Mayo Otterloo fund management group in Boston and for years a voice that counselled caution, wrote late last month. "Now, finally, they are cheap and likely to get cheaper. Likely, I believe, to set up a once-in-a-lifetime investing opportunity (or maybe twice in a long career)."

He is only starting to buy, however, and has not deployed all the cash he has available. Buying now makes sense for those truly in it for the long term; the bottom may still be ahead.

W hen markets experience dislocations as extreme as Black October, as Mr Buffett implies, what is important is the mass psychology reflected in the market's moves.

Indeed, there are ways to assess investor psychology. The Chicago Board Options Exchange's Vix index, for instance, measures "anxiety" from how much investors in options are prepared to pay to protect against future falls in the S&P 500. This measure was not around during previous great bear markets but the spike in volatility in recent years took it to all-time highs. When sentiment becomes this extreme, it is fair to hope that stocks have become too cheap, creating bargains once confidence returns.

Looking instead at realised volatility, or the extent to which stocks vary on a monthly basis, the S&P last month was as volatile as it had been at any time since 1929, except October 1987. All previous spikes in volatility returned swiftly to calm.

Yet another measure comes from US Treasury bills, short-term loans to the US government that are arguably the safest investments in existence. When T-bill yields fall, investors are prepared to pay more for that safety. At the worst of the recent panic, T-bill yields reached 0.02 per cent, their lowest since 1940. They have barely recovered. Again, such an extreme desire for security might imply that the market cannot fall much further and is ready to swing in the other direction.

A further measure, comparing the yields available on the highest-rated - triple-A - bonds with bonds of only slightly lower quality once again shows the desire for safety leaping to extremes not seen since the 1930s.

A popular model - although academics suggest that it is flawed - compares the yields on stocks to the yields on bonds. The model does have a kernel of common sense. When bond yields are very low, as they are now, that could signal that it makes sense to pay more for stocks, in search of a higher return.

There is therefore a respectable case to be made that in the past few weeks fear has conquered greed to an extent that goes beyond the rational. The return of stability in due course creates the opportunity for a big rally. But this may merely be a "bear market rally". In the past two weeks, the S&P both staged its 20 per cent revival and then gave up half of it. That is not surprising - the bear market after 1929 was punctuated by several rallies of 20 per cent or more.

A market bottom cannot hold if stocks remain too expensive, so long-term measures of valuation have proved to be great indicators of bear market tops and bottoms. One suggested in the 1930s by Benjamin Graham, an investment theorist, looks at cyclical price/earnings ratios, where the price of a stock is compared with the average of the earnings per share it has produced over the previous 10 years. This controls for the effect of the profit cycle, which otherwise would mean that year-by-year multiples tended to be higher when profits were at the low point of the cycle and lower when profits were high.

This measure has been revived by Yale University's Robert Shiller, who gained fame for publishing Irrational Exuberance, in which he warned that stocks were badly overvalued, shortly before the internet bubble burst in 2000. Enhancing that fame in recent years have been his indices showing that another bubble, in US housing, was about to burst. Shiller p/e multiples reached their greatest extremes in 1929 and 2000, two market tops that were followed by bear markets. In October 1987 they peaked at a much lower level, giving an important clue that the market break of that year would prove to be less significant. Further, the lows have coincided with long-term market bottoms. There is also a tendency to revert to the mean over long periods.

Significantly, the cyclical p/e now suggests that stocks are slightly cheaper than their long-term average, for the first time since 1991. That in turn implies that those who can afford to wait a number of years for a pay-off should start to feed money into the stock market.

A variation on this theme is to look at very long-running trends. There are various ways of doing this, but Mr Grantham's simple model holds that over time, stocks rise by inflation plus 2 per cent. This produces an upward trend line, to which stocks will eventually revert. On this basis, stocks have recently snapped back to fair value, having been wildly overpriced. As with the cyclical p/e model, this suggests that the stock market had been overvalued since 1991.

(to be continued)

在上月全球股市暴跌之际，沃伦•巴菲特(Warren Buffett)的最新言论足以安定人心：他宣布正在买入股票。人称“奥马哈圣贤”的巴菲特称：“一条简单的原则决定着我的买盘：在别人贪婪时，我恐惧；在别人恐惧时，我贪婪。”巴菲特指出：“毫无疑问，恐慌正到处蔓延，连有经验的投资者也不能幸免。”没有人会对此表示不同意见。但是，显而易见的极端恐慌情绪，未必说明股市已经触底。巴菲特在为《纽约时报》撰写的专栏上也承认这一点，他建议投资者根本不要在入市时机上费神。他的意思是，现在股价很便宜，人们不应承担等待的风险。

巴菲特写道：“对于股市一个月或一年后会上涨还是下跌，我一无所知。但很可能发生的情形是，远在市场情绪或经济好转之前，市场就已走高了，也许幅度还会相当大。因此，如果你等待知更鸟，春天就将过去了。”

然而，有没有办法判断股市是否已经触底？当然，在恐慌盖过贪婪到这种地步时，根据基本面来评估股票价值是行不通的。相反，人们只能从历史得到借镜。然而，像上月的“黑色十月”这么极端的情形在历史上鲜有先例。全球最受关注的基准指数——标普500指数自去年10月达到历史最高点后，已下跌了46%。在过去100年里，只有4个时期的跌幅能够与之相比，其中两次出现在上世纪30年代。

在最近一次大跌后的几周内，标普指数一度反弹20%之多，但其后呈现震荡走势。全球几乎所有其它股市走势相似，跌幅甚至超过美国，反弹幅度也大于美国，之后又都陷入横盘格局。

没有人认为，市场有丝毫恢复正常的迹象。股市崩盘后的几周内，外汇市场上演了历来最严重的崩盘；信贷市场状况变得更加严峻。历史数据同样不祥：1929年大崩盘之后，在市场刚开始企稳就买入的投资者，在其后两年内损失了逾四分之三。

一辈子只有一次的投资机会

但有些人已开始抛下恐慌。波士顿基金管理集团Grantham Mayo Otterloo的创始人、多年来一向奉劝投资者谨慎行事的杰里米•格兰瑟姆(Jeremy Grantham)上月末写道：“过去20年是空前的，全球股市受到了高估，尤其是美国股市。现在，终于，它们变便宜了，而且可能变得更便宜。我相信，这可能带来一辈子只有一次的投资机会（对于从业较久的人来说，或许一辈子能遇上两次）。”

不过，他只是刚开始买入，而且也没有满仓。对于真正作长线投资的人来说，现在买入有其道理；但底部或许尚在前方。

当市场像“黑色十月”如此剧烈震荡时，正如巴菲特所言，重要的是市场走势所反映的大众心理。

的确有一些方法可以评估投资者心理。例如，芝加哥期权交易所(CBOE)的Vix指数，就根据期权投资者愿意支付多大成本对冲标普500指数的下跌风险，来衡量市场的“焦虑”程度。在以往大熊市期间，这一指数尚未问世。但近年市场波动加剧，该指数迭创新高。在市场情绪变得如此极端时，的确可以认为，股价已变得过于便宜，一旦信心恢复，就会构成不可错过的好买卖。

再来看实际波动情况，也就是股市单月波动程度，除了1987年10月以外，标普指数上月的波动幅度大于1929年以来的任何时候。以往，股市波动性在飙升后往往迅速回稳。

投资者惧怕风险

另一个衡量标准是美国国库券，也就是美国政府借入的短期贷款，眼下它堪称最安全的投资品种。当国库券收益率下跌时，投资者愿意以更高的价格买入这种安全资产。在近期恐慌情绪最严重的时候，美国国库券收益率达到0.02%，为1940年以来最低，目前也几乎没有回升。对资金安全的渴望达到如此极端的程度，或许也预示着市场不会进一步大跌，而是即将掉头回升。

还有一个衡量方法是比较评级水平最高的债券（即AAA债券）与质素稍逊的债券之间的收益率，它同样显示投资者对安全的渴望是上世纪30年代以来最强烈的。

一个流行的模型是比较股票与债券的收益率。尽管学术界指出该模型存在缺陷，但该模型的核心概念确实与常识相符。当债券收益率像现在这样很低时，那就可能意味着，为了获得更高的回报，增加对股票的投资是合理的。

因此，我们可以得出这样一个合理的结论：近几周来恐慌已压倒贪婪，已经到了超出理性的地步。有朝一日市场回稳，会为大反弹创造机会。但这也可能只是“熊市反弹”。最近，标普指数先是反弹20%，接着又失去一半回升幅度。这不足为奇。1929年后的熊市就曾数度反弹20%甚至更多。

从长期估值看股价吸引力

如果股价仍偏高，市场就无法维持在一个底部上，因此，长期估值方法被证明是透视熊市顶部和底部的有效指标。上世纪30年代，投资理论家本杰明•格雷厄姆(Benjamin Graham)提出，应观察周期市盈率，即股价与前10年每股平均盈利的比率，藉此控制利润周期的效应，因为在一个利润周期中，当利润处于谷底时，按年计算的周期市盈率往往较高，当利润处于高位时，该比率就较低。

耶鲁大学的罗伯特•席勒(Robert Shiller)重提上述衡量方法。席勒因著有《非理性繁荣》(Irrational Exuberance)一书而声名大噪。2000年网络泡沫破裂前不久，席勒就在该书中警告，股价被严重高估。近年席勒的名声更响，他编制的指数预示了另一场泡沫即将破裂，那就是美国的房地产泡沫。1929年和2000年，席勒的市盈率倍数分别达到极端最高值，股市都处于顶峰，也都很快迎来熊市。1987年10月，该指数于较低的水平见顶，这是一个重要的信号，预示那年市场暴跌的影响不会很大。此外，该指数的低位与市场在长期内的底部相吻合。而且，在长期内，该指数呈现出回归均值的趋势。

值得注意的是，周期市盈率表明，目前股价比长期均值略为便宜，这是1991年以来的首次。这意味着，那些能够为了得到回报而等待多年的人应当开始将钱投入股市。

在此基础上，可以看非常长期的趋势。这有许多种方法，但格兰瑟姆的简单模型认为，从长期看，股价将以通胀率加2%的幅度上涨。这就产生了一条向上的趋势线，股价最终会回到这条线上。以此来看，曾被大幅高估的股价近期已回归合理价值。与周期市盈率一样，该模型也显示，自1991年以来，股市一直被高估。

（待续）