The younger generation is simply not having children at the high rate of previous generations.
Anecodotally, most of my mid 30's friends have either 0 or 1 child, a few that got started earlier have two.
On the other hand, the millions of legal and illegal immigrants, especially from Latin America, are keeping the birth rate up. They do, in fact, many times live in much more crowded conditions. I have met a few Hispanic immigrants in my area as I speak Spanish, and in each case, they lived in single family homes with multiple families / generations.
Anecodotally, most of my mid 30's friends have either 0 or 1 child, a few that got started earlier have two.
On the other hand, the millions of legal and illegal immigrants, especially from Latin America, are keeping the birth rate up. They do, in fact, many times live in much more crowded conditions. I have met a few Hispanic immigrants in my area as I speak Spanish, and in each case, they lived in single family homes with multiple families / generations.