编者按：我对于历史会否重复的观点一直持保留态度，因为作为一个交易者/投资者，研究这些东西其实并无实战帮助。我觉得我们要做的是把握中长线的重要支撑(周线/月线)并做好对冲，以及短线支撑(日线)并做好止损，就可以了。除了看以下的有趣信息，大家可以看一下这两张标普500的周线图，第一张是截至到目前的Apr.14.2014这一周的，第二张是Nov.2. 2007 那一周的，那个礼拜之后发生的事情大家都知道了，可是Apr.14.2014这一周之后发生的事情谁都不知道。这就是股市的魅力，是否有点“前不见古人,后不见来者。 念天地之悠悠，独怆然而涕下”的感觉？哈哈。

截至到目前的Apr.14.2014这一周之前的标普周线图

Nov.2. 2007 那一周之前的标普周线图

Source：Short side of long

As the month of March posted its final closing print for the S&P (at over 1,880), the equity market participants celebrated five year bull market anniversary (from March '09 to March '14). Ironically, majority of them most likely missed the first few years and have been pilling into the trend as of late. How typical. Conversely, I feel that the opposite course of action might be prudent and here are just a few simple reasons why.

Chart 1: This is the second longest bull market in the 80 year history!

 Source: Short Side of Long

According to historical data, the current US equity bull market is the second longest in the last 80 years and third longest in a 100 year history (as the roaring 20s hold close similarities to the roaring 90s). As we can see in Chart 1, over the last several weeks, the current bull market has edged out the infamous 1982-87 and 2002-07 bull markets in terms of length.

A keen student of historical market trends should be able to observe that each and every prolonged bull market (which builds financial and economic excesses) does not usually end with mild correction, but rather serious market re-pricings. In other words, just as majority of the retail investors are becoming confident with stock investing once more (slowly forgetting the lessons of 2008), history shows us that risk increases substantially as the trend ages. Consider the following:

• 1920s bull market lasted 8 years and crashed by almost 90%
• 1980s bull market lasted 5 years and crashed by 40%
• 1990s bull market lasted almost 8 years and eventually crashed by 50%
• 2000s bull market lasted 5 years and crashed by 50%

I am not necessarily predicting another monster crash, but what I am trying to put forward is the notion that the longer the bull market goes on for, the higher the excesses become and the more painful the clean out could be on the other side.