Earlier quoted context omitted.
Why? Don't really follow your logic. My hypothesis is that women (specifically teenage girls) just aren't interested in the field / profession so they decide not to study it in school or search for jobs in the field. Perhaps this is because they are discouraged from trying it by their teachers or media, perhaps its because they don't have the confidence to believe they'll succeed, perhaps they think it's not cool, pe…
The "aren't interested" hypothesis would also need to explain why the physical sciences haven't had the same decline in involvement as computer science nor why there is a specific decline in participation in computer science but not in the other categories. I don't think anyone is afraid to suggest that girls aren't interested in the field, it's just that it is a very unsatisfying answer and it doesn't really make se…
I agree that it is strange that the drop isn't as large as it is for women in STEM in general, but I don't think it disqualifies the hypothesis.
I guess from my perspective if you only have a handful of women even entering a CS department in university in the first place, then the first and most important problem to solve is why they don't seek to study the major, or participate in high school programming classes. I believe if you can answer that question and remove that factor, it will be the biggest first step.
Disclaimer: Was a CS major, dated a CS major woman who coached me through Calculus and who I collaborated with in software classes. I'm biased.