The world population is only rising because India/China/Africa.
Here in the US, my two kiddos are in public elementary school classrooms with 10 kids. When I went to school, it was ~30 to a class. Millennials born 81-95 were the children of the boomers. But on average, we're not having nearly as many kids as our parents did.
A "big family" today means 2 kiddos. Moms are frequently having only one due to explosive costs, or none at all.