[arialeks]

If given the choice people will usually pick the field they find interesting. If however you live in an impoverished country where getting a job in a STEM field could be the ticket out, you are way more likely to consider picking those fields. My (original) country is rather poor for example, but the education is free and a lot of people in college that were studying with me picked EE & CS just because it could give them a good paying job, they didn't care about the field nor did they in most cases enjoy it all that much, those who didn't change their mindset usually didn't graduate or it took them more because they were forcing themselves, anyhow in those living conditions the male to female ratio in STEM fields was always close to 1 : 1. But that might not be the case were OP lives, because in a rich country people get to choose with far less pressure and in the end it still holds true that most girls just don't find those fields to be interesting.