Squeak, thank you for your response.
Why would you say it gets much narrower?
Based on data from The World Factbook (yes, I originally found it on Wikipedia).
You’ve agreed to the basic equation, you’re just saying that migration could mitigate or eliminate the disparity. Hamotzi meichaveiroi alav haraya.
It’s also against an almost universally observed phenomenon, and every possible migration you mention is counterintuitive.
If anything, more boys seem to go otd or migrate to
non shidduch communities, and more girls seem to become bt.
You’ve mentioned litvish girls marrying chassidish boys before. The notion if that having any serious affect on the demographics is so far fetched to me that I literally thought it was another one of your faked moon landing bubbe maisas.
B’kitzur, the notion of these migrations is highly unlikely to have any significant effect on the disparity which it seems you agree would exist without migration, so even though it’s not 100% muchrach, it’s worth working with the fairly safe assumption that the observed disparity isn’t merely an illusion IF there would be no negative side effects.
That’s a big IF, though, but I’ve not really commented much on that aspect of it. We might agree on that issue.