The popular rule is simple: buy what members of Congress buy and avoid what they sell. I tested it on 17,859 common-stock disclosures filed under the STOCK Act from January 2020 to August 2025 (27,790 trade lines, 1,601 stocks), entering at the first close after each filing became public and comparing against the S&P 500 over the same dates. The rule fails, and the reason isn't the reporting delay.

After Purchases vs S&P 500 Beat the index Sales vs S&P 500 Beat the index

1 month -0.52 pts 47.0% -0.54 pts 47.0%

3 months -1.79 pts 45.0% -2.22 pts 43.8%

6 months -2.63 pts 44.1% -4.06 pts 41.8%

1 year -5.36 pts 42.9% -6.39 pts 41.3%

Medians of each disclosure's return minus the S&P 500 over identical dates. Both directions rose in absolute terms (about 11% after a year); the index rose more.

Five findings

1. Buys don't beat sells. On the 760 filing dates with both purchases and sales, the one-year buy-minus-sell spread was 1.13 points with a t-statistic of 1.15. At one, three and six months it was zero.…