None of this happens in isolation. The people who have no children don't hide in their basements... they're out there in public, teaching the children of others

None of this happens in isolation. The people who have no children don't hide in their basements... they're out there in public, teaching the children of others how awesome it is to be childless. Or, if I'm less hyperbolic, being the wrong sort of role model. If they convert children more quickly than others can have them, then this still goes downhill. How do you even model that? Is it fertility rate - conversion rate = 2.1? I suspect that conversion rate to be significant. I'd be shocked if it's not closing in on 1.0 (or already blown past it). We can do a gutcheck mental exercise here. The Duggars have 20ish children. Will they reach 400 grandchildren, or even come close?