$SPX Monthly: In attempt to discover things that I may easily miss in a fast moving market, I am in the process of writing an "Auto-Fib" study that draws long and short Fibonacci pullbacks using past pivot levels where the 61.8% line is not broken. In the process of testing the study in various markets and various timeframes, it is proving to do what it's intended. (I wish I had this study months ago!!!)
One thing I hadn't noticed before is that the March 2009 low lines up incredibly well with the 0.618 pullback from 8/1/1982 low to all time highs. This is a situation where this bullish retracement remains valid until that 0.618 level is broken (which it hasn't). (Of course, I say "bullish" in the context of 20+ years of data.) See chart below. This prompted me to have a closer look at the 50% level (839.15). See second chart below...
An aside, notice the 50% short at the 1121.44 area.
$SPX Daily: The two levels mentioned above are placed below on the daily chart. Notice the 50% level at 839.15. On 10/10/2008 we hit this area for the first time and hit a low of 839.80! Almost exact! We then immediately rallied ~205 points to 1044.31. The 0.618 level gave us our March low and, so far, has given us twice the bounce at ~408 points. Hmm...
$INDU Monthly: Of course, this prompts me to look at the Dow and see if there was a similar reaction. In the Dow's case, the measurement was from the 10/20/1987 low (bottom of the 1987 crash) to highs (20 years later, to the month, on 10/11/2007). The 50% and the 61.8% levels also marked significant levels (however, not quite as exact as the S&P). Scroll down for daily chart...
$INDU Daily: For completeness sake, here are the two levels mentioned above, drawn on the daily. Yes sir, the market is just unpredictable randomness! ;]