Have you also considered a possibility that there is no explanation, and the gap is simply due to internal variability in the underlying dynamical system?
Although personally I favor the "different interests" explanation, let me expand on this a bit. Humans love explanations, even of random events, that's how superstition comes about.
There was an interesting biological experiment done with ants. If you put two identical piles of food the same distance from an anthill, you would intuitively expect that ants will eat from each pile in 50/50 ratio. However, it's not what happens; in reality, the ratio fluctuates over time, at points being 20/80 and can reverse to 80/20.
Why? Because behavior of each ant depends on strength of pheromone path to food that is produced by other ants. In other words, ants, to some extent, copy behavior of other ants. And this copying is enough to produce a large difference in ratio even in cases that are objectively absolutely equal.
So is it hard to conceive that humans also copy behavior of other fellow humans (actually, the above example is from Paul Ormerod's book Butterfly Economics), and that women might prefer a job where already are other women? Or where isn't an overwhelming majority of different people (i.e. men)?
The influence on individual decision can be very subtle, but yet can, statistically, lead to large differences in outcome.