The reason the percentage of women drops off has nothing to do with sexism, and everything to do with women's choices.
If you have children, you want to have a healthy work/life balance. Most women choose, therefore, quite reasonably, to work part-time or not at all. Inevitably, this means that men, on average, end up earning more overall. It's nothing to do with pay inequality. Pay inequality doesn't exist in the West.
I also take issue with those who say that we should balance the numbers of different kinds of people in the population with the numbers admitted. If 70% of white men, for example, apply to Apple, that doesn't mean that Apple should try and take on 70% of white men. There should simply be no quotas whatsoever. One year, you may get an unusually talented group of black Ethiopians; another year, you may get a group of talented Japanese women. You may get ten years in a row of talented white students from Yale, simply because a combination of innate talent and good education led to that.
Whoever is most talented should get hired, and that's the end of the story. It doesn't matter if you have freckles or hairy toes; you just need to be the best man for the job.
You bring up some interesting points. Where I live, in Maryland, I have noticed that approximately 90% of all medical office staff, nurses, and eldercare workers I see are black, and many of those are black first generation immigrants from various countries in Africa. About 70% are women. I have also been to a fair share of black doctors and seen an increasing number of black medical technicians and paramedics. My ob/gyn who delivered my daughter is a black woman. We also have a lot of black clergy divided almost equally between men and women (from what I have seen): my minister who performed my marriage ceremony is a black woman.
Yet as far as I know, nobody has raised a fuss about that. There have been no articles that I have run across (not saying none exist, I just don't see it making the headlines) and no studies done to explain why there are not more non-blacks in these very lucrative medical professional jobs that pay well, offer stability and good benefits and decent hours.
As a minority woman I'm really not going to freak out that there aren't as many minority women or women in general working as programmers and developers or tech entrepreneurs, where the hours can indeed be brutal and take you away from your family, when clearly there are opportunities in these other lucrative fields that are more family friendly for women (and men who wish to be heavily involved in day-to-day child rearing) and clearly welcoming to minorities. These are good paying solid jobs requiring intelligence and proficiency and do not consign anyone who works at them to a permanent underclass. Indeed, the healthcare sector is growing and workers in this sector can keep networking, upgrading their skills and education and look forward to a bright future. If black people are embracing opportunities here, they are smart to do so.
As long as the women and minorities who do have an interest in technology jobs have fair access to the education that would prepare them for tech careers and have fair access to the jobs, I have no objections to the current demographic breakdown among tech industry workers.
It is up to parents and educators to ensure, however, that math and science and tech jobs are not seen as purely the domain of whites or men. As a mom and aunt, I have had to overcome subtle biases introduced via the marketing of children's books, toys and science kits. This post is already long so I won't elaborate on that for now.
At any rate, we should break down artificial barriers to career choices like that, and in the process, make sure we don't erect any barriers in the future that might be detrimental to white men and women seeking opportunities wherever their talents lead them. I hope in the future people don't look at certain careers and think "Oh that's men's work. Or women's work. Or a black job, or a white job or a Hispanic job." It should be an opportunity, period.