The Deterrent Effect of the Securities and Exchange Commission's Enforcement Intensity on Illegal Insider Trading: Evidence from Run-up before News Events

We examine whether public enforcement of US insider-trading laws affects price discovery. Examining insider-trading civil cases filed by the Securities and Exchange Commission (SEC) from 2003 to 2011, we find that the price impact on insider-trading days is much smaller than the effect documented for the 1980s, consistent with increased fear of prosecution. Moreover, we find that preannouncement anticipatory run-up in comprehensive samples of takeover bids and earnings announcements is negatively related to resource-based measures of public enforcement intensity, which suggests that aggressive SEC enforcement deters illegal activity. In addition, we find that quoted bid-ask spreads are negatively related to the SEC's enforcement intensity, which suggests that greater enforcement improves liquidity. Moreover, the negative and significant relation between run-up and the SEC's enforcement intensity persists after controlling for quoted spreads.