道指暴跌是否预示凛冬将至？回顾那些历史上的熊市

10月10日，道琼斯工业平均指数的跌幅达到了800点。同日，标普500指数也下跌近5%。这是否预示着美国股市一个具有历史意义的大牛市即将终结？

股市是周期性波动的，一个节点是否是由牛市转向熊市的拐点，只有进入了熊市之后才知道。目前，在整个股市的增值部分中，有相当一部分由以苹果公司为代表的科技股主导，光是苹果一家的市值就超过了万亿美元。在大盘普遍下跌的背景下，一些人对科技股尤为精神紧张，加剧了短期的暴跌。另外，美联储加息和就业的紧缩也让投资者信心不足。

根据一些权威定义，所谓“熊市”，是指标普500指数至少要比牛市的顶点下跌20%以上；同理，所谓“牛市”至少要比熊市的最低点上涨20%以上。很多股市观察人士认为，美股的本轮牛市由2009年3月9日起，到2018年10月10日止，是二战以来为期最长的一次，持续了3503天。到8月22日，它已经打破了“史上最长牛市”的纪录——此前的纪录是从1990年10月到2000年3月。

从历史上看，二战结束后，几乎所有的熊市都始于持续而显著的下跌，而不是简单的波动。当全球金融和政治局势不稳定时，美股的跌幅可能会达到5%甚至10%以上，但之后就会出现类似幅度的上升。而熊市则是从持续的均匀下降开始的。

因此，在接下来的几周至几个月里，需要关注的迹象并不是股市的波动性，而是要观察任何一段四到八周的时间里，市场的平均下行趋势。

比如在1973到1974年的股灾中，标普500指数于1972年12月达到峰值——也就是700点左右。此后至1973年10月，标普500指数平均每个月下降1或2个百分点，总体跌幅达15%。随后突然暴跌，到1974年9月又跌了40%，此时已经触底。此后，标普500指数直到1987年才恢复到700点。

自1975年以来，按通胀调整后的股市市值已经增长了很多，不过每次熊市也再没出现过那么大的跌幅。而且熊市后的牛市会快速收复失地，并且超过熊市前的顶点。

牛市经常会因为一个决定性的事件而结束。比如1956年，美联储启动加息，同年又发生了苏伊士危机和匈牙利革命等事件，导致了投资者纷纷撤资。1987年10月19日是美股历史上著名的“黑色星期一”，这一天，美股单日跌幅超过20%，此前股市的强势反弹在波斯湾危机和贸易赤字的夹击下迅速化为泡影。

上一轮牛市是2002年10月到2007年10月，由于通胀以及大量次级贷和其他不良贷款的发酵，这一轮牛市的崩溃迅速引发了全球性的金融危机。

值得欣慰的是，和牛市相比，熊市总是短暂的。最近的一轮熊市始于2007年，只持续了两年半左右。不过此后的牛市却足足花了四年的时间，才追上了2007年的最高值。（财富中文网）

译者：朴成奎 

The 800-point drop of the Dow Jones Industrial Average on Oct. 10 may be a blip, and so could the nearly 5% decline over five days in the S&P 500. But they are also possibly leading indicators of the end of a historic bull market, in which stock-market indexes continue upward quarter after quarter.

Markets are cyclical, and experts only agree after the fact on what predicted an oncoming bearish period (and even then, often not). And right now tech stocks—like the trillion-dollar Apple—have dominated a significant part of the rise in value of the market as a whole. Jitters about those companies have led to this short-term fall, too, while drops were felt throughout the market. Rising interest rates from the Fed and a tight employment market don’t reassure investors, either.

A bear market by many definitions requires a drop of at least 20% in the S&P 500 from a bull-market peak; likewise, a bear market starts counting at a 20% rise out of a deep trough. Many stock-market observers pin the start of the current bull market, the longest since World War II, at March 9, 2009. As of October 10, it’s lasted 3,503 days. On August 22, it exceeded the previous record length, which ran October 1990 to March 2000.

Historically, almost all bear markets since World War II have started with consistent and significant ongoing declines, rather than simple volatility. Drops of 5% to 10%, or even higher, can occur during global financial and political uncertainty, but they’re paired with similar rises. Bear markets start with consistent average drops.

So, signs to watch for in the upcoming weeks and months aren’t volatility, but an average tendency for the market to head downward across any four-to-eight week period.

In the 1973–74 stock market crash, for instance, the S&P 500 peaked around 700 in December 1972, and then dropped a percentage point or two almost every month through October 1973, a 15% decline overall. But then it plummeted, crashing another 40% by September 1974, when it bottomed out. The index didn’t reach 700 again until 1987.

Bear markets since 1975 have had far lower percentage drops at their bottom, even as markets have grown remarkably in inflation-adjusted dollars. The following bull upswings more quickly regain lost ground and then exceed pre-bear highs.

Bull markets tend to end because of a defining event. In 1956, the Fed raised interest rates, while international events like the Suez Crisis and the Hungarian Revolution caused investors to pull back. In 1987, stocks dropped more than 20 percent on a single day—Black Monday, Oct. 19—after a strong rally crashed into the Persian Gulf turmoil and trade deficits.

The previous bear market, from October 2002 to October 2007, collapsed in the face of the global financial crisis, precipitated by raising interest rates in the face of inflation that revealed the vast scale of subprime mortgages and other badly collateralized loans.

The good news? Bear markets are short compared to bull runs. The most recent, starting in 2007, lasted about 2 1/2 years, though it took another four for the bull market to exceed highs reached in 2007.