Sorry, even if it is somewhat true all over the western world (it is certainly in terms of quality, at least), you can't make a global study just out of Perth.
Perth is a region which lives on the mining industry. Therefore, lots of guys from everywhere head there to make big bucks. So it's absolutely normal there is such an unfavorable ratio there. It's the same in every places where there are so many jobs that only men can perform (oil & mining): northern Alberta (Canada), North Dakota (USA), Middle East, Mongolia, etc., you name it.
Perth is a region which lives on the mining industry. Therefore, lots of guys from everywhere head there to make big bucks. So it's absolutely normal there is such an unfavorable ratio there. It's the same in every places where there are so many jobs that only men can perform (oil & mining): northern Alberta (Canada), North Dakota (USA), Middle East, Mongolia, etc., you name it.