There is also opportunity cost. If a couple has 20k+ to spend a year on child care, that means they have enough free money that they can do a lot of other enjo

There is also opportunity cost. If a couple has 20k+ to spend a year on child care, that means they have enough free money that they can do a lot of other enjoyable things instead. Airplane fares keep decreasing, destination vacations are becoming more and more affordable, and "everyday luxuries" keep being pushed down into becoming more affordable. Or to put it another way, having a kid means a serious drop in QoL compared to being a DINK. 60 years ago this didn't matter, even the upper middle class wasn't jetting off around on a regular basis. Also it wasn't as socially acceptable, all your friends were having kids and if you didn't have kids you were missing out. Compared to now when there are basically two parallel societies, families with kids and families without kids, and one can choose which group to be a part of.