Do you mean to tell me that DEMAND is the largest influence on market share?? Who would have thought? God forbid the government know anything you could learn in Economics 101.

I'm a female engineer and a member of the Society of Women Engineers where I get exposed to a lot of the outreach and networking activities going on to encourage young women to get interested in science and to retain female engineers already in the workforce. From my POV, I see the possible causes of this downturn as:
1. Outsourcing/The Economy: Fewer students are pursuing degress in engineering and computer science because there aren't jobs for them when they graduate. Women are not blind to the writing on the wall and can apply their skills elsewhere.
2. Industry Environment: Businesses, especially tech businesses, function on processes and rules based on how men think and operate. Most of those businesses are not receptive to new ideas and changes to the way they operate. Also, when the economy takes a plunge like it is now, diversity programs are usually some of the the first to be cut.
3. Work/Life Balance: Women who choose to have a family will always struggle with the stressful demands of many IT and engineering jobs. Even a few weeks of maternity leave can put you way behind in your career, much less taking more time off to stay at home with kids. The industry is not set up to allow women to handle that kind of time off and still be competitive for raises and promotions.
4. Individual discrimination: Despite #2 and #3, the biggest threat to women in engineering is not instititionalized sexism, but individuals who make it difficult to thrive in an engineering job on a daily basis. If I had a nickel for every time one of my coworkers talled me "sweetie" or "darlin'" or compared me to and treated me like their daughter instead of their colleague (I AM their daughters' age, but come on guys, a little respect please!), I would have quite a large pile of nickels. :-P
5. Outreach programs targeted exclusively at girls in college are implemented TOO LATE: If you don't get them interested in math and science by the 5th grade, there's little chance that they're going to change their minds later. By the time students get into high school and college, they already have a general idea of what they're going to do. Since I'm involved in SWE, I have a direct impact on changing this trend, and we do a lot of work with our local Girl Scouts and other K-12 outreach organizations as well as networking with college students for retention purposes.

That's my $0.02. Right now the biggest factor for me personally is #1: how can I encourage girls to go into science and engineering fields when outsourcing makes my own job security a myth? I'm considering going back to school for a graduate degree in medical device engineering because I don't forsee my job in computer design sticking around for much longer...