If you are not able to assure that you'll have a comfortable retirement years with the appropriate social safety nets to try to assure that someone who worked will be able to maintain at least the basic necessities for life, then having kids who make it into adulthood is that safety net.
The "ok, 60+ years old, unable to do meaningful work, move in with a successful child" is a fairly standard approach. This requires that you have kids and preferably enough that one of them will be able to support you moving in with them and isn't otherwise alienated from you.
Note that this only works on a per family basis and if you outlive your children (war can do that), then a more nationalized social safety net is something that because useful to have. By providing that safety net for retired adults, there is less pressure to have kids to support their parents in retirement and less pressure for single people to marry and have a family to fulfill that role.
Economic hardship (increasing the pressure to not have kids) and that safety net (reducing pressure to have kids at all) in both would then have downward force on the fertility rate and also would suggest putting off having kids until later.
Also of interest - Multigenerational family structure in Japanese society: impacts on stress and health behaviors among women and men - https://pubmed.ncbi.nlm.nih.gov/15087144/
If you are not able to assure that you'll have a comfortable retirement years with the appropriate social safety nets to try to assure that someone who worked will be able to maintain at least the basic necessities for life, then having kids who make it into adulthood is that safety net.
The "ok, 60+ years old, unable to do meaningful work, move in with a successful child" is a fairly standard approach. This requires that you have kids and preferably enough that one of them will be able to support you moving in with them and isn't otherwise alienated from you.
Note that this only works on a per family basis and if you outlive your children (war can do that), then a more nationalized social safety net is something that because useful to have. By providing that safety net for retired adults, there is less pressure to have kids to support their parents in retirement and less pressure for single people to marry and have a family to fulfill that role.
Economic hardship (increasing the pressure to not have kids) and that safety net (reducing pressure to have kids at all) in both would then have downward force on the fertility rate and also would suggest putting off having kids until later.
Census.gov has a lot of interesting data for the rate - https://www.census.gov/library/stories/2022/04/fertility-rat...
Also of interest - Multigenerational family structure in Japanese society: impacts on stress and health behaviors among women and men - https://pubmed.ncbi.nlm.nih.gov/15087144/