Ekkehart Boehmer, Charles M. Jones, Xiaoyan Zhang
This is a great article, there is a new version out published in Journal of Finance, Vol63: Issue 2, April 2008 couldn’t find it though.
Abstract
We use a long, recent panel of proprietary system order data from the New York Stock Exchange to examine the incidence and information content of various kinds of short sale orders. Since 2000, more than 12.9% of NYSE volume involves a short seller, suggesting that many market participants are able to surmount any short-sale constraints that might be present. As a group, these short sellers are extremely well-informed. Stocks with relatively heavy shorting underperform lightly shorted stocks by a risk-adjusted average of 1.25% in the following 20 days of trading (16.9% on an annualized basis). We partition short sales by account type: individual, institutional, member-firm proprietary, and other, and we can tell if a short sale is part of a program trade. Institutional non-program short sales are the most informative. Compared to stocks that are lightly shorted by institutions, a portfolio of stocks most heavily shorted by institutions underperforms by a risk-adjusted average of 1.54% in the next month (over 21% annualized). Large short sale orders are the most informative. In contrast, when more of the short sales are small (less than 500 shares), stocks tend to rise in the following month, indicating that these orders are uninformed. The reported alphas do not account for the cost of shorting, and they cannot be achieved by outsiders, because the internal NYSE data that we use are not generally available to market participants. But these findings indicate that institutional short sellers have identified and acted on important value-relevant information that has not yet been impounded into price. The results are strongly consistent with the emerging consensus in financial economics that short sellers possess important information, and their trades are important contributors to more efficient stock prices.
Link to article