This has happened to every single society [*] as it industrializes [0], and offering extensive support and incentives to parents (e.g. as has been tried in Scandinavian countries) does very little to reverse this trend [1, 2]. My hypothesis is that as societies industrialize, they afford their population more and more activities that are simply more fun and rewarding than having children. So many people I know put of…
We're having kids in our 40s when our parents started in their 20s. We're naturally less able to have as many because menopause kicks in.
There are no easy answers here. Younger pregnancy limits education and careers.