Trying to get back to birthrates …
Interesting cite over here:
My summary of the article cited in that post:
A study found that the advent of smartphones in 2007 just cratered teen and barely-20 pregnancies in the USA. While having much smaller effects in the older cohorts. Now, 20 years later, the effects remain strong in the now-young cohort but somewhat diminished in the then-young, now late child-rearing age cohort.
Meta-point: Teen pregnancies are were, and have always been, a meaningful fraction of total pregnancies. Achieving replacement fertility without significant teen pregnancy is very difficult and perhaps impossible absent coercive means.