that’s it
so basically very few people - as in both partners - were consciously planning kids, they were just having sex, but the irresponsibility was curbed by nature, sanitation, as many of the resulting children died.
of the people that were planning children, they also has to hedge with many dead children, but suddenly they were all living
so now people had to plan for the consequences and post 1950s the planning resulted in real practical choices, where people realized they dont want children.
people never wanted the consequences of having children or many children. the history corroborates this. when both parties are now choosing
the incentives haven’t helped for that reason
the incentives are all based on the assumption that family planning is difficult and out of reach. merely delaying something desired, when they just won’t accept that most of has just don’t want children and never did.
we still have sex. the decline in that amongst always single people is new, just the last several years. couples do the things that make children all the time, and just don’t get pregnant or output children.