[theragra]

Afaik according to research, the only thing that helps is

1. Lump sum, pretty big (like year worth of salary or close) payment on birth

2. Works for first child only.

That's it. So, it kinda works, but very limited. Increasing sum did not increase birthrates, if I remember correctly.

[myrmidon]

This sounds extremely plausible to me, but I would be very careful about conclusions from such studies, because I believe the general expectations of society as a whole regarding child-raising matter a lot and you can't easily quantify that.

Anecdotally, when my grandmother did not birth a child for two consecutive years in her thirties the village priest came to investigate (!!). Expectations have shifted massively since, and the single/dink lifestyle is way more "acceptable" now.

[lokar]

And often the payment merely changes the timing of the child