NATIONAL BUREAU OF ECONOMIC RESEARCH
NATIONAL BUREAU OF ECONOMIC RESEARCH

Decoding Inside Information

Lauren Cohen, Christopher Malloy, Lukasz Pomorski

NBER Working Paper No. 16454
Issued in October 2010
NBER Program(s):   AP

Using a simple empirical strategy, we decode the information in insider trades. Exploiting the fact that insiders trade for a variety of reasons, we show that there is predictable, identifiable “routine” insider trading that is not informative for the future of firms. Stripping away these routine trades, which comprise over half the entire universe of insider trades, leaves a set of information-rich “opportunistic” trades that contains all the predictive power in the insider trading universe. A portfolio strategy that focuses solely on opportunistic insider trades yields value-weight abnormal returns of 82 basis points per month, while the abnormal returns associated with routine traders are essentially zero. Further, opportunistic trades predict future news and events at a firm level, while routine trades do not.

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Document Object Identifier (DOI): 10.3386/w16454

Published: “Decoding Inside Info rmation” (with Christop her Malloy and Lukasz Pomorski), 2012. Journal of Finance 67, 1009-1044.

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