It’s no secret that members of Congress qualify as political insiders, but a new report strongly suggests that they also may be insiders when it comes to trading stocks.

An extensive study released Wednesday in the journal Business and Politics found that the investments of members of the House of Representatives outperformed those of the average investor by 55 basis points per month, or 6 percent annually, suggesting that lawmakers are taking advantage of inside information to fatten their stock portfolios.

“We find strong evidence that members of the House have some type of non-public information which they use for personal gain,” according to four academics who authored the study, “Abnormal Returns From the Common Stock Investments of Members of the U.S. House of Representatives.”