That’s the preliminary conclusion of a study conducted by researchers at Stanford University and the University of Chicago, who say that on average, women in Congress introduce more bills, attract more co-sponsors and bring home more money for their districts than their male counterparts do.

The study, which examined the performance of House members between 1984 and 2004, found that women delivered roughly 9 percent more discretionary spending for their districts than men…

Researchers say the small number of female members may have something to do with their effectiveness. Women who run and win are likely the most politically ambitious and talented of their pool, having potentially overcome hurdles including voter bias and self-doubt about their ability to win. Female candidates also tend to attract more challengers. Politically eligible women tend to doubt their ability to get elected and raise money more than men do, multiple studies have indicated. Large majorities of both men and women in candidate feeder pools, such as law offices and political organizations, believe there is a bias against women in elections, according to Lawless and Fox studies in 2005 and 2004.