Historically, a number of 50% or more has marked tops in the stock market. Furthermore, bullish sentiment has been elevated for an extended period of time indicating that retail traders are very bullish. Since this is a contrarian indicator, it would suggest that now is not the best time to be long stocks. That being said, AAII sentiment has not been very helpful during the last 4 weeks. It has remained extremely bullish for some time and yet the market has continued to climb.
Here is a short-term chart of AAII sentiment.
Click chart for larger image.
Here is a longer term chart which compares AAII bullish sentiment with the S&P 500
Here is a chart which compares AAII bearish sentiment with the SP 500.
Black Swan Insights
AAII Sentiment Down Despite Strong Market--Oct 14,2010
Marc Faber's October Outlook