This paper estimates the performance of insider trades on the closely held Oslo Stock Exchange (OSE) during a period of lax enforcement of insider trading regulations. Our data permit construction of a portfolio that tracks all movements of insiders in and out of the OSE firms. Using three alternative performance estimators in a time-varying expected return setting, we document zero or negative abnormal performance by insiders. The results are robust to a variety of trade characteristics. Applying the performance measures to mutual funds on the OSE, we also document some evidence that the average mutual fund outperforms the insider portfolio.

This paper estimates the performance of insider trades on the closely held Oslo Stock Exchange (OSE) during a period of lax enforcement of insider trading regulations. Our data permit construction of a portfolio that tracks all movements of insiders in and out of the OSE firms. Using three alternative performance estimators in a time‐varying expected return setting, we document zero or negative abnormal performance by insiders. The results are robust to a variety of trade characteristics. Applying the performance measures to mutual funds on the OSE, we also document some evidence that the average mutual fund outperforms the insider portfolio.