S&P 500 10-Day A/D Line: Extreme Oversold Readings

Heading into Monday's open, the 10-day A/D line for the S&P 500 is at -1,696 which is the eleventh lowest reading in the last ten years. The charts below compare the S&P 500 to its 10-day A/D line.  In the lower chart, red circles denote every daily occurrence where the 10-day reading was below -1,500, while in the top chart the red circles denote the first occurrence during each period where the 10-day A/D line was below -1,500.  As one can imagine, the days after 9/11 include 10-day A/D line readings of -1,500 or less, but what is somewhat surprising is that the first occurrence of -1,500 occurred the day before on 9/10.