I see they are taking birth rates as a basis. That assumes that all the children they have will follow their parents' religion. I don't think that can be taken for granted. When I look at my own country it seems that people are less and less following their parents' religious choices. Most Catholics in Holland of my generation are only so in name. That say they are to please the parents, but they don't do anything ch…
Haredim society is more like the Amish, everything is tightly integrated. Far less Amish leave the church and community.
But young people live in a more open world. The ones that still adhere to such strict rules are a tiny minority.