Copying Congress after disclosure: a pre-specified event study of congressional purchases, 2020-2025

Members of the US Congress must report their stock trades within 30 days of learning of them and no later than 45 days after the trade. I ask whether an outside investor who buys what members bought, once the purchase is disclosed, earns an abnormal return. Using 3,942 purchases of US-listed common stock by 124 House members from 2020 to 2025, of which 3,903 enter before the price data end, I form a portfolio that holds each stock for 62 trading days from the first trading day after its purchase is disclosed. This test, specified before any return was estimated for this study, gives a Carhart four-factor alpha of -1.63% a year (t = -0.66, p = 0.51), with a 95% confidence interval from -6.5% to +3.2% a year. Buying at the open of that day, which an outside investor could execute, gives -1.66% (t = -0.67). The result holds across alternative holding periods, entry prices, factor models and samples, and none of the planned event-level tests yields a statistically significant abnormal return after correction for multiple testing. Across all House trades in the sample, the median trade was disclosed 13 days after it was made, and 6.6% were disclosed more than 45 days after the trade. Use of AI tools: I used Claude (Anthropic) to assist with writing the manuscript and the analysis code. I reviewed all text, code and results and take full responsibility for the content.