—a whole flock of rugrats are much less attractive when you don’t need them for subsistence agricultural help or to replace those lost in the hunter-gatherer culture-—
Yep, declining birth rate is an inevitable result of children becoming an economic burden rather than benefit.
We’re not going to be going back to an unmechanized agriculture society anytime soon.
Any attempt to drastically shift tax burdens from families to the childless more than they already are is going to be political suicide for the party that attempts it, as it will enrage the childless.
And some sort of religious theocracy that bans the pill would also be futile. Nothing would be easier to sneak across the border.
That “pack of rugrats” is the only way to perpetuate your culture. Imports from Mexico or Somalia may fill schools and take jobs, but bring enough of them and you won’t have America anymore — you’ll have Mexico and Somalia on formerly-American soil.
For the young very wealthy, four or more children are the ultimate status symbol. For the very poor, such fecundity is the source of great government benefits.
For the in-between, kids are by usually—though not universally—wanted, and they are a major cost and a big drag on lifestyle until the grandparenting years.
As has been noted by others, when the completion of grad school is considered prudent before settling down, there are far fewer peak years of fertility before pregnancy and birth become significant medical challenges.