@CBUK2K2 I can see that I am not going to convince you and that is OK. I am an engineer with a teenage daughter and am involved with a number of organisations who support women in STEM and support girls in STEM subjects in schools. We see lots of factors which impact how women and girls choose their subjects, their careers and their career progression.
There are a huge number of societal factors involved at every stage. Girls arrive at school believing they are just as good as boys but quickly lose that belief, it is not just school that feeds that loss of self belief. When we have quotas for accelerated math programmes on a state wide level, we see higher drop out rates for girls, when we have girl only programmes, they stay. Women only research teams are more productive than mixed or male teams but when it comes to funding, male teams or teams with a male at the head of the team attract more funding. At many points along the journey, people look for behaviours that they associate with success rather than success itself and until we see successful well paid women in all areas, we will not see women follow them.
Things haven't changed in engineering and computer science since I was at university but we need women in these careers to ensure we are building a future world that fits us all rather than a male perspective of what is needed.
I don't believe the gaps are due to women opting out of these paths voluntarily, but due to the fact that it is not a level playing field. It is easier for a mid performing boy to stick with computer science through university and to find a job than it is for a high performing girl. The decision to give up work or take a career break to have children is not equal between men and women and usually comes at the end of battles to have your work recognised, to stake your claim in the boardroom, to then find that it is not easy to keep your career and family plates spinning, often its the last straw rather than a new choice made in a vacuum, and women take time out believing it's a pause and not a derailment, and underestimate the challenges of returning to work.