My favorite memes on this topic are:
If there were such a wage gap, companies would just hire a much larger proportion of women to save costs. Companies care about money, not being sexist.
Best explanation for the gap:
Women value things like family time more than men, so they work less hours (less overtime), don't go into as stressful of positions (also lower paying) - this includes things like college degree choice - they will pick liberal arts far more often).
More often a question of personality. If he challenges you on something specific like a certain company with the same position - imagine this situation in which the boss asks from 3 people to stay late and work on a stressful task - just based on personality, it's more likely that a man chooses to do so. There are big societal differences between men and women which is fine, but there's nothing stopping them from stepping up to fill that role. This happens on a large scale.
Also women work more part-time jobs, take more vacation time and sick leave. And maternity leave. As a result, men accumulate seniority much faster, and earn more
Wages are on a bell curve OP. While men are more likely to have a higher paying job than women, they are also more likely to have a shitty fucking job strong, empowered wombans would consider beneath them.
If you rally for more women CEOs you better rally for more women sanitation workers.