Political Insider Trading: A Narrow versus Comprehensive Approach

Abstract

We examine senators’ electronically filed stock transactions between 2012 and 2019 to assess the extent of politician’s insider trading. Our results suggest that senators use inside political information when investing and earn significant market-adjusted returns. To extend traditional return-based methods, we propose a new comprehensive approach based on abnormal idiosyncratic volatility (AIV), which captures the degree of information asymmetry around their trading dates. We document that senator trades are associated with substantially high levels of AIV, suggesting that they represent only a tip of the iceberg, since the mass of unfiled transactions using the same inside information remains undetected.

Keywords: Abnormal idiosyncratic volatility, legislator’s trading, politician’s insider trading, STOCK Act

JEL Classification: C58, G12, G14, G28