Why are there only 16 million Jews in the world? Did they all get fixed or something? It has been nearly 80 years since the lost 6 million. In the intervening years, why have they not been fruitful. Or are the numbers lies?
Marriage to non-Jews might be an explanation. They may have progeny, but have not stayed with that religion. Or, like most folks these days (aside from Muslims), they just have one or two. Our culture doesn’t approve of lots of kids.