“For women, at times, it’s, ‘Carry your own water,’ but this is a business that you can learn a lot from people who have been around the block,” Mr. Gompers said. “I don’t think it’s conscious gender discrimination, but I do think in many of these firms, it just happens because our natural tendency is to associate with people who are like us.” Mr. Gompers was a paid witness in Kleiner Perkins’s defense during the trial.

The researchers analyzed all venture capital investments from 1975 to 2003, using data from VentureSource. They controlled for characteristics like investors’ education and work experience and the industries in which they invest.

Jennifer Fonstad, a founder of Aspect Ventures and former partner at Draper Fisher Jurvetson, said that the results did not necessarily match her experience, and that the data was probably skewed by the small number of women, the years covered and the difficulty of attributing investments to certain partners. “There are things happening in real time in the field much more quickly than in the data, and there is much more success on the venture side than the data shows,” she said.

Still, in surveys with 93 female venture capitalists for the Harvard study, 59 percent said they felt they had been disadvantaged because of their gender. About a third said they received less informal feedback than their male colleagues did, and about a quarter said they had not benefited as much as men from mentorship. They were less likely to go fly fishing or biking with a colleague, or get advice during a casual office chat.

But women at larger, older firms or at those with other female investors were less likely to feel disadvantaged, particularly in the area of informal feedback from colleagues.

The dynamics, of course, vary by firm. Kleiner Perkins is an older, larger firm. Several people testified in the Pao trial that Kleiner Perkins did not have enough formal policies, including one on sexual harassment, and that women were excluded from informal meetings.

Though the study showed the benefits of formal processes, venture firms and start-ups sometimes view these as a waste of time. Small firms often have no human resources employees, and when they do, they are focused almost solely on recruiting.