仍然看好股票牛市的投資者都是在玩火。因為熊市的警告信號已經出現，它就像沙漠中的火花一樣脆弱。
最大的警示來源於“高低邏輯指數”。Norman Fosback於1979年創立了該指數，隨後由經濟研究協會主席及現任Fosback基金預報的編輯加以完善。該指標描述的是紐約證券交易所兩組數據中較小的值，這兩組數據指的是52週新高和52週新低（都用所占交易量的百分比來表示）。
因此，該指數可以解決内部市場分歧。Fosback在他的投資教程《股票市場邏輯》中說明了原因：“在常規狀況下，大量交易要麼創下新高，要麼創下新低，兩者不會同時發生。一個健康的市場需要内部統一。”
通過這一方法可以判斷出，當前的股票市場一點也不健康，10週移動均線達到了5.7%，已經高出了很多研究者的賣出信號閥值。（以Fosback為例，他的閥值是5%，他認為超過這個閥值就預示著“極端市場分歧…甚至熊市”。Ned Davis研究、Venice研究以及弗羅裡達研究公司的閥值是4.4%。）高低邏輯指數顯示出了這麼危險的信號，為什麼沒人在意呢？原因有二：
首先，該指數更善於追蹤長期趨勢而不是短期區間，而且它的信號不夠成熟。舉例來講，在2007年-2009年的熊市之前，自十月起，高低邏輯指數打破了六月底的五個閥值。所以一些人雖然擔心高低邏輯指數，但仍要等到其他指數確認之後才會採取行動。
另一個原因是該指數在2013年給出了一系列錯誤信號。如圖所示，該值在2013年夏天已經漲到了6%，但牛市根本沒有結束。
你也可以看出高低邏輯指數在去年年底攀升得更高，在12月底達到了6.9%。雖然我現在知道道瓊斯指數下跌了，但那時誰也不知道這是否仍是個錯誤信號。
Leuthold 集團的投資總監Doug Ramsey特別擔心高低邏輯指數傳遞出的消息。他指出，幾年前錯誤信號占據主流位置，而當前的納斯達克市場卻有著極大的分歧。
事實上，Ramsey指出，自2007年起，納斯達克版本的高低邏輯指數首次超過了“賣出”閥值。我不會告訴你那時發生了什麼。
Opinion: Stock market bulls are playing with fire
Published: Aug 18, 2015 5:15 a.m. ET
CHAPEL HILL, N.C. (MarketWatch) — Investors who are giving the bull market in stocks the benefit of the doubt are playing with fire. That’s because the bear market’s warning signals have created a situation as vulnerable to the slightest spark as a parched desert.
The latest warning comes from the so-called High-Low Logic Index. That well-regarded indicator was created by Norman Fosback in 1979, then the president of the Institute for Econometric Research, and currently editor of Fosback’s Fund Forecaster. The index represents the lesser of two numbers
The indicator, therefore, is a measure of internal market divergences. In his investment textbook “Stock Market Logic,” Fosback reasoned: “Under normal conditions, either a substantial number of stocks establish new annual highs or a large number set new lows — but not both. ... A healthy market requires some semblance of internal uniformity.”
By this measure, the current stock market is anything but healthy. The 10-week moving average of weekly readings recently rose to 5.7%, well above the level that many researchers use as the threshold for a “sell” signal. (Fosback, for example, set this threshold at 5%, considering readings above that level as evidence of “extreme market divergence and ... bearish.” The threshold employed by Ned Davis Research, the Venice, Florida-based research firm, is 4.4%.)
Why hasn’t this dangerously lofty level of the High Low Logic Index received more attention? There are at least two reasons.
The first: The index has a better track record over longer, rather than shorter, spans, and its signals can be premature. Prior to the 2007-2009 bear market, for example, which began in October, the High Low Logic Index breached the 5 threshold in late July. So it’s possible that some of the bulls are worried about the High Low Logic Index but are waiting for confirmation from other indicators before pulling some of their chips off the table.
The other reason that some are ignoring these latest warnings is that the index gave a number of false signals in 2013. As you can see from the accompanying chart, in fact, it rose to near 6 in the summer of 2013. (I wrote a column reporting its dangerously high level in August of that year.) Needless to say, the bull market didn’t soon come to an end.
You’ll also notice from the chart that the High Low Logic Index rose to an even higher level at the end of last year — hitting 6.9 in late December. It’s too early to know whether that, too, will prove to be a false signal, though I would note that the Dow Jones Industrial Average is lower today than it was then.
One adviser who is particularly worried about the message of the High Low Logic Index is Doug Ramsey, Chief Investment Officer of The Leuthold Group. He points out that, unlike the situation that prevailed on the occasion of those false signals a couple of years ago, this time around there also is extreme divergence in the Nasdaq market, in particular.
In fact, Ramsey reports that a Nasdaq-only version of the High Low Logic Index just rose above its “sell” threshold for the first time since 2007. I need not remind you what happened at that time.
本文翻譯由兄弟財經提供
文章來源：http://www.marketwatch.com/story/stock-market-bulls-are-playing-with-fire-2015-08-18