I think that having fewer children is a worldwide trend. It's the same here in my country. In my grandparents' time, people had lots of children, even though life was harder than it is today. Today, people have 1 or 2 children at most. I agree with everything you said, like when you have several children, some take care of the others. Having just one child requires more attention from the parents and there's no one to share that attention with when you only have one child.