Short Selling Around Seasoned Equity Offerings

61 Pages Posted: 25 Mar 2008 Last revised: 3 May 2017

See all articles by Tyler R. Henry

Tyler R. Henry

Miami University

Jennifer L. Koski

University of Washington - Michael G. Foster School of Business

Date Written: September 15, 2008


This paper uses daily short selling data to examine whether short selling around seasoned equity offerings (SEOs) reflects informed or manipulative trading strategies. We find no evidence of informed short selling around SEO announcements. Around issue dates, higher levels of pre-issue short selling are significantly related to larger issue discounts, consistent with manipulative trading. These results are significant only for the non-shelf registered offerings in our sample. We also directly test the effectiveness of SEC Rule 105, and find that it constrains some but not all manipulative trading. This research makes three main contributions to the literature. We are the first paper since the SEC implemented rules restricting such behavior to provide direct evidence that pre-issue short selling is associated with larger SEO discounts. Previous research using monthly short interest data rejects the manipulative trading hypothesis. Our results differ from prior research primarily because daily short selling data allow much more powerful tests. Second, our evidence that there is no manipulation around shelf offerings provides one possible explanation for the increased popularity of shelf registrations. Finally, although short selling usually enhances price efficiency, we document a situation where short selling makes prices less efficient.

Keywords: Seasoned equity offerings, short sales, Rule 10b-21, Regulation SHO, Rule 105, Informed Trading, Manipulation

JEL Classification: G14, G32, G38

Suggested Citation

Henry, Tyler R. and Koski, Jennifer Lynch, Short Selling Around Seasoned Equity Offerings (September 15, 2008). AFA 2009 San Francisco Meetings Paper. Available at SSRN: or

Tyler R. Henry

Miami University ( email )

Oxford, OH 45056
United States

Jennifer Lynch Koski (Contact Author)

University of Washington - Michael G. Foster School of Business ( email )

Box 353226
Seattle, WA 98195-3226
United States
206-543-7975 (Phone)
206-685-9392 (Fax)

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