This comic should be required reading: http://www.smbc-comics.com/index.php?db=comics&id=1883#comic
The presence of trans people backs this up: MtFs are overrepresented in tech, and the ratio of MtFs to FtMs in tech is about the same as the ratio of cis men to cis women in tech (I am MtF myself, and it's a running "joke" in the trans community that trans girls are all programmers). If you have the tech skills and the drive to work in the industry, you'll do fine here regardless of whether you're male or female. It's just that if you spent your childhood and teenage years being perceived as a girl, then you're supremely unlikely to even be an applicant to a tech position. At that point, there's nothing the tech industry can do to change anything.
Also, one thing I've observed is that if you're a nerd, non-nerdy boys are more likely to say "whatever floats your boat", and non-nerdy girls are more likely to say "eww, gross!". Peer pressure is the worst kind of pressure.
1. Tech is lowest on the totem pole in middle and high school. Nerds are bullied, ostracized, and generally considered uncool.
2. Girls in school are more susceptible to social pressure than boys.
I think 1) and 2) together reliably explain why there aren't many women in the tech industry. It's not the industry's bias, it's society's bias. So the correct steps (in my opinion) would be
1. Stop glorifying sports and start glorifying tech more. The math olympiad team at high schools should be lionized more than the football team.
2. There is no step 2)