Fewer women in computer jobs these days

When I was an undergrad at Washington University in Saint Louis, the number of women majoring in Computer Science was approaching 50%. Now, as someone who teaches CS, I note that the percentage is much, much lower. Often, there are only one or two women in the classes I teach --- sometimes none. And I don't think it's just me. This eventually translates into fewer female computer professionals, as the referenced article describes. In 1983, when I graduated, over 30% of computer professionals were women; in 2002, only a bit over 27% were. I suspect that the percentage today is even lower. Note that this is counter to gains that women have made in natural sciences and other engineering disciplines. What is it about the computing that is different than other technical disciplines? I don't see how it can be the subject matter. Whatever the cause, the profession and society are all the poorer for the lack of diversity of ideas behind the products we make and the research we do.