[x3iv130f]

My 10 cent hypothesis would be social detachment leads to falling birthrates.

It is well known that people don't have the same strong community bonds to those in the same physical space that they used to.

In an environmemt like this sex becomes rarer and riskier as partners are more unknown.

Giving birth and raising children also feels riskier as individuals don't have a community to rely on and absorb the added burden of child rearing.