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Lessons From Single-Company Event Studies: The Importance Of Controlling For Company-Specific Events, Scott D. Hakala

Scott D Hakala

Single-company event studies are commonly employed in applied practice, such as in analyzing market efficiency, reliance, and damages in securities litigation. However, the presence of significant company-specific events among the observations used to estimate the market model results in significantly biased, overstated standard errors (a well-known omitted variables problem) and less reliable coefficient estimates in such studies. This is a frequently over-looked or neglected issue that renders the statistical inferences in single-company event studies employing using more traditional event study techniques biased and often unreliable. This paper demonstrates through simulation and actual examples that, even allowing for errors in implementation, …