Women make up about one-fifth of Congress. They are just as poorly represented as witnesses in congressional hearings. According to a study from the Sunlight Foundation, women account for 23 percent of the witnesses of the more than 5,500 witnesses that have testified before House committees in the 113th Congress. Agriculture, Transportation, Armed Services, Financial Servies all faired the worst, with fewer than 17 percent women. Education and the Workforce had the best ratio, of 40 percent female.

As the Washington Post's Colby Itkowitz pointed out yesterday, this disparity is not just evident in Congress, but also at the top of Fortune 500 companies and in Cabinet positions.

It's possible that the male-dominated witness stand is simply a reflection of the ratios of Congress, and that even fewer women have leadership roles as chairs. Only one out of 20 chairs is a woman. Sunlight did not compare how the Republican-controlled House fared against a Democratic one. So, Democrats' witness ratios could be just as bad, or worse. 

But it could also be that the gender balance—or imbalance—of these hearings reflect the ideological direction of Republican politics. There are a number of cases over the last few years when Republicans held hearings about women's contraception or abortion rights that happened to include only men. An all-male panel testified on birth control in 2012, after House Oversight Republicans rejected the Democratic witness Sandra Fluke as "unqualified." A similar situation happened again last year at a House event in favor of tightening abortion restrictions.