Answer: Females.
The simple answer to all these bait questions is that women can and do have children, which is time consuming and whether people deny it or not, mothers are far more integral in raising a child than fathers.
Naturally, spending less time in the workplace leads to them falling behind even though they might have started on equal or greater footing as their male counterparts.
You might want to revisit your thinking.
Yes, career trajectories can be impacted by childcare. But that doesn't explain everything. Other cultures where sexism isn't as prevalent (e.g. Soviet Russia, which despite all of its failings did impressive engineering), we don't see these kinds of statistics.
Why is it so hard to accept that sexism exists, and that it has a negative impact?
I think it should be considered that all the talk about sexism in IT causes confirmation bias in people and they are more likely to falsely attribute their decisions to it.
This difference reverses later in life