Here’s a fascinating finding from Nate Birkhead about gender, partisanship, and ideology in the U.S. House of Representatives. As measured by DW-NOMINATE scores, Republican men and Republican women are the same. But Democratic women are much more liberal than their male counterparts:
The next step that it would be interesting to see is whether this is just a coincidence in which no women Democrats represent the kind of districts that tend to elect moderate Democrats. You could compare everyone’s DW-NOMINATE score to their district’s PVI and see if there’s a gender gap in representation.
[UPDATE] According to Brian Frederick’s 2009 study, “Are Female House Members Still More Liberal In a Polarized Era” (PDF) this effect goes away when you control for underlying district partisanship.