This particular indicator is a ratio of odd-lot short sales compared with odd-lot stock purchases. It is an attempt to measure the sentiment of smaller, unsophisticated investors.
This is a five-year chart of weekly postings showing the S&P 500 in black and a 16-week moving average of odd-lot short sales/odd-lot purchases in red. The green lines relate to the three-year average of this indicator and the corresponding standard deviations.
The first thing to note is the tremendous increase in the ratio over the five-year period. Odd-lot short sales have increased dramatically, while odd-lot purchases have remained relatively static.
The puzzling thing is that I would think hedge funds would generally trade in round lots and wouldn't have much effect on this indicator. But the more I have studied this, the more I have to conclude that there has been enough of an increase in hedge fund shorting to move this indicator in a major way (perhaps because they are placing odd-lot orders in conjunction with their round-lot short sales, i.e., 250 shares). So, in a way, this indicator has changed and will probably not decline again to levels reached in 2002. There is no clear high or low value now.
The other thing to notice is how shorting picks up dramatically with every market correction. The level of this indicator goes to new highs with every new small decline. It is as if these short-sellers use any market weakness to put on short positions for a major market decline.