David Hirshleifer is Professor of Finance at the University of California, Irvine. This post is based on an article authored by Professor Hirshleifer and Usman Ali, Portfolio Manager at MIG Capital. Related research from the Program on Corporate Governance includes Insider Trading via the Corporation by Jesse Fried (discussed on the Forum here.)
In trading their firms’ stocks, insiders must balance the profits of informed trading before news, the scrutiny by regulators that such trading can engender, formal policy restrictions by firms of insider trading activities, and diversification and liquidity motivations for selling shares after vesting of equity-based compensation. This mixture of motivations and constraints makes it is hard to decipher the information content of insider trades, especially because different trades may be intended to exploit news arriving at short or long horizons. This noise makes it feasible, up to a point, to conceal deliberate opportunism from regulators such as the SEC.
Empirically, there are some indications that insiders do exploit private information. Past research finds that insider purchases positively predict subsequent abnormal returns. On the other hand, effects are much harder to identify for insider sales, presumably because such sales are often performed for non-informational reasons, such as to reduce risk or to consume.