If you've been browsing the internet reading about women in engineering recently, chances are you've seen one of the articles that talk about the NSF/ University of Wisconsin - Milwaukee study which found that only 62% of women with engineering degrees are working as engineers. The presentation is actually quite interesting, so you should give it a look. The study included female alumnae from the 30 universities with the most engineering graduates, and from the feedback snippets in the linked presentation- it seems like they got some pretty honest feedback.
So while I'm not affiliated with this study in any way, I'd encourage you to participate and send it to your friends (male and female) in engineering. As you already know, having a complete data set is important for ensuring accurate results, and studies like this have the potential to help our field evolve. I'm one of the 62% of women who are still engineers, and I for one would love to see an environment where people are happy enough to stay.