If 1 million women were coding, then 100 billion men started coding, those 1M women would still be coders. So there wasn't necessarily a decline. Or maybe there was, and the numbers will reflect that.
I am interested in the actual numbers, not graphs or interpretations. But I've never found a data source, so hopefully someone knows of one.
The whole debate is interesting because there are at least four separate sides: men who don't believe it exists, men who recognize it as a systemic problem, women who believe it's the most important aspect, and women who wish the debate would go away so they can focus on doing good work instead of on doing good work as a woman.
Me, I don't know enough about it. I'm just curious about the numbers over time. And if I have a daughter hopefully I'll think of some crafty way to make programming seem interesting. The one badass female dev I know said she regretted not getting into it from a younger age, so it seems worth fixing.