It seems to me that you are considering only symptoms of more underlying driving forces here. For example: Why is it that they don't show up at the Java User Gr

It seems to me that you are considering only symptoms of more underlying driving forces here. For example: Why is it that they don't show up at the Java User Group? Maybe they feel uncomfortable in a room with 95% men? Then you would have to explain why there are 95% men in that room in the first place. Women probably get promoted relatively earlier for reasons like token women and the fact that they less commonly have computer experience since early on.