In response to:"The fact that women are so underrepresented in many STEM fields indicates that there must be some educational, societal, or institutional force pushing them away." Emphasis added

There is. It has a lot to do with women though. First with STEM, the hierarchy in the workforce always favors the smartest/most knowledgeable people. This means you can't flirt your way to the top or simply just "make it" eventually.

The work is somewhat quantifiable, so people can be tracked in how much work they do. You can't sit around and chat or take extra time off and fuck around. People will find out.

Many fields have horrible deadlines and any person not finishing their work on time can slow an entire project and become the weakest link. When you're holding up something that thousands of people are working on, relying on, etc and they're all waiting for you, not fun. Additionally you'll be pushed to do overtime, heavy overtime. When it comes to software development for example, in the last few months leading up to release, you'll be better off bringing extra clothes and a sleeping bag to work. This can apply to virtually all other fields in different ways for different reasons.

Women and men study differently. Women are great and memorizing but don't focus on understanding. This is why there's a relatively equal amount of girls/boys in STEM the first year, but then it significantly favors the boys as time passes. The problem is that women do great on tests, but don't bother to understand that knowledge, which is fairly important later on and everything you learn will be used in the future (as you move from first to 4th year). This is why girls have been doing better (or so it seems) ever since standardized tests.

There are no problems in STEM for women. There's nobody out there trying to hold them back. My university cracked down hard on this shit, even had security cameras installed to ensure there was no harassment or sexism going on. And you know what changed? Nothing.

The key is attacking gender issues from both sides, rather than the BS of encouraging women to enter and just ignoring all problems men have.

What exactly is there to attack? There's 50% more women in college than men. Women have infiltrated every major out there outside of STEM. Do you know how HUGE STEM is? Let me tell you how huge it is. Go look up any non STEM focused University out there (MIT or Standord) and check the faculty for STEM or other majors. You'll find out quickly that the entire STEM curriculum has fewer faculty than a single major like business.