Chinese women have been sharing their experiences receiving phone calls from government workers and officials, during which they are asked invasive questions about family planning and whether or not they are pregnant.
At this point the culture had shifted to not value large families and so few even think it is possible while not having kids seems like a valid option. It takes years to shift this even with an effort to encourage kids.
If it was just that, surely there’d be a rebound visible on the chart after 2016 (8-year-olds and younger)? Instead it falls off even harder
They can’t get married till they have a house, and there are problems there…
At this point the culture had shifted to not value large families and so few even think it is possible while not having kids seems like a valid option. It takes years to shift this even with an effort to encourage kids.
Not making your society a dystopian hellscape might help.