It may be worth exploring the gender differences that may exist between different types of institutions (e.g., Very High Activity Research Universities, Master's Universities/Colleges, Diverse Bachelors/regional universities). It may be that women are less represented at the highest research activity universities, but more represented at regional universities. Women at lower profile institutions may be making a very reasonable decision on how to allocate their time commitments. The relative valuation (towards tenure/promotion) of presentations versus posters may be larger at the research university, but treated as no difference at a regional university (as is actually the case at many smaller universities). For instance, I am at a regional university where, for my department, there is no difference in credit (towards tenure/promotion) given between a poster presentation and an oral presentation (regardless of length). Therefore, for me to maximize my time investment for the reward I get, a poster is usually the way to go.