Option traders are considered among the most informed investors because their trades strongly predict future stock returns. We identify the source of their information edge using a quasi-exogenous shock to insider trading enforcement. With the arrest of Raj Rajaratnam, prosecutors launched an...

We train a machine learning method on a class of informed trades to develop a new measure of informed trading, the Informed Trading Intensity (``ITI''). ITI increases before earnings, M&A, and news announcements, and has implications for return reversal and asset pricing. ITI is effective...