Raising her first major funding round for her then three-year-old shipping and data company last year, Shippo Chief Executive Officer Laura Behrens Wu came to an uncomfortable realization: pitching any of Silicon Valley’s rare female venture capitalists gave her more anxiety than pitching men.

“They do harder due diligence, making sure they’re not going to embarrass themselves,” Behrens Wu recalled. “Maybe they have a chip on their shoulders?” she asked. “I empathize with women VCs, in an environment where they’re constantly trying to prove themselves.”

She ended up raising her $7 million round from investors like Albert Wenger at Union Square Ventures and Jeff Clavier at SoftTech VC. While she has some money from women investors, it was at the earlier “seed” stage, where people typically invest a few thousand dollars with minimal commitment.

Observers who lament the lack of women at Silicon Valley startups have placed much of the blame on male venture capitalists, who mostly back companies started by other men. If more women worked as venture capitalists, the logic goes, they would encourage and invest in more women-founded companies.

A new Bloomberg analysis shows this isn’t necessarily true, at least at 17 top venture firms. Those with senior women partners backed companies founded or co-founded by women at roughly the same rate as firms with no senior women partners. (The group of 17 top-ranked venture firms is based on $1 billion-plus public offerings or acquisitions over the last five years for U.S.-based portfolio companies invested in at early stages, according to data provided by CB Insights. “Senior partner” was defined as a U.S.-based partner eligible to hold a board seat and take a portion of the profits known as carry; because that information is often confidential, Bloomberg had to rely on data provided by the firms.)

And a Bloomberg analysis of the top 10 private companies founded or co-founded by women, ranked by Pitchbook by funds raised, showed that none had raised money from a female venture capitalist as a young company, defined as the venture stages known as Series A or B. They include Kabbage, Boston-Power, the Honest Co. and 23andMe.

The issue matters because of fairness, and because the venture business, where white and Asian men dominate, could be missing opportunities to fund more types of outstanding companies. “Attracting and backing the best entrepreneurs and businesses is the main reason” to encourage good representation of women venture capitalists, said Dayna Grayson, an investing partner at NEA.

Her firm is one of the top seven with at least one senior woman investing partner based in the U.S. NEA has invested in the most female founded or co-founded U.S. startups, with 30. Founders Fund also had a strong showing, with 19, as did Kleiner Perkins Caufield & Byers, with 13. However, these firms also represent some of the world’s biggest venture funds, with the most partners overall. Many firms declined to give the number of their active current investments, making a comparison of their total percentage of female-founded startups impossible.

Some of the most female-founder friendly firms have no senior female partners, or in some cases, no female partners at all. When adjusted to compare the numbers of women co-founders to the number of senior partners overall at any given firm, Felicis, Lowercase, Index Ventures and First Round Capital had the highest proportion of support for women founders. None of those have senior women investing partners, although Felicis Ventures employed one, Renata Quintini, until she left for Lux Capital earlier this year.

Unlike Grayson, most of the women partners at the top firms back just a few women-founded companies, if any. In many…