贴一张Murphy图

http://stockcharts.com/h-sc/ui?s=$SPX&p=M&yr=10&mn=6&dy=0&id=p23288151497&a=127028169&listNum=3

MONTHLY BANDS GIVE DOWNSIDE TARGETS ... Chart 2 applies "monthly" Bollinger Bands to the S&P 500 for the last ten years. The middle (dashed) line is the 20-month moving average. [Daily, weekly, and monthly Bollinger bands use 20 as the default value]. Focus on the 20-month average first. Notice that it acts as an excellent support line during major uptrends (1997 to 2000 and 2003 to 2007) and a bearish resistance line during major downtrends (2000 to 2003). There have been only two crossings of that line in the last eight years -- a downside crossing in 2000 and an upside crossing in 2003. Each correction in the last five years has bounced off that support line. Chart 2 shows, however, that the 20-month (or 400-day) average is being tested once again. A decisive close below that line would be taken as a major bear signal. How much could the market drop if that were to occur? That's where the lower Bollinger band comes into play. A decisive violation of the middle line usually leads to a drop to the lower band. At the moment, the lower bands sits at 1267 (and rising). A drop to the lower band would represent a decline of 20% from the October high. That would qualify as an official bear market. Chart 3 adds another piece of information supporting a 20% decline from the recent peak. The horizontal lines represent Fibonnaci retracement levels. In a downtrend, a market will usually retrace at least 38% of its previous uptrend. Chart 3 shows the 38% retracement line coinciding with the lower Bollinger band. That doesn't mean the market can't drop further. But that's a minimum downside target. And I think we're heading there.