Education time and income instability. People are well into their 30s before they know where to settle down after finishing an education. They're well into their 40s before they can afford to.

If any country wanted to increase childbirth rates, they ought to lower working time, increase education pay and move employment out of the central cities.

Or put simply: Money and time needs to be available for the people they want to reproduce.

Now, I just saw the latest Kurzgesagt episode on this, and there's one thing they missed: Automation. We don't necessarily need to keep a stable or increasing population if only we can automate a lot more labour. In my opinion it's the only solution to avoid the future population crisis.