But does that mean women are self-selecting women and there is bias against males in those fields? It depends on who you ask.
People rarely admit to bias and in 2015 people are rarely overtly biased, so instead it may be that when you walk into a classroom and no one looks 'like' you, you may be uncomfortable or, worse, you may feel like you are representing your whole gender/ethnicity and under-perform because you worry about how it makes your group look if you fail.
Is such stereotype threat real? Hard to say but the social sciences swear by it. How much of it is instead rationalization - I got a bad grade or did not get a job or a grant because of issues that are outside my control - and how much is real is difficult to determine when some people are clearly using statistics for their cultural agenda. If smart women go into medicine but not physics, does that mean physics blocks out women? Does it mean the social sciences regard female doctors as so mentally weak they couldn't function unless half the class was men?
Outside academia, what does the public think? In some countries in Europe, they do think science is more for men, which we can logically assume might be a problem for women. An association test (Project Implicit) of ~350,000 self-selecting participants from 66 countries found that various cultures regard science as more of a 'male' occupation.
Holland had the most bias, with Denmark, Belgium and Sweden also showing rather poorly.
Anyone in science, and at least a few in the social sciences, recognize the flaws in an implicit association test (you are racist/sexist, the only question is how much) much less a self-selected one, which obtains participants by recruitment, media coverage, etc. and lacks any controls. The authors tried to factor that out using multiple selection criteria but they still undermine their efforts by implying causation and the slippery slope of social science logic knowing its flaws - if a young female thinks science is only for men she may not go into science. But what that does not tell us now is how much of it is just old people, who are also more inclined to be racist and politically immovable, and whether or not that makes any difference at all in the thinking of young people setting out on their educational paths.
So the study has a giant flaw though the results make common sense - the good news is the gap has been narrowing for some time. Yes, academic science used to be mostly male, and they have tenure, but when women apply for new/open faculty jobs, not only do they have an equal chance, they are actually over-represented. But as the only gender who has kids, the obstacles are usually in place before it comes tenure time - when it comes to family balance and careers, academia has a long way to go before they catch up to the private sector.
How did America do? The U.S. may be the source of chronic complaining by racist, sexist, unhinged sociology professor criminals, but it does pretty well when it comes to perceptions of scientists; 35 percent of kids picture a female.
Not perfect, but not as bad as Switzerland or those other European countries either.