The simple answer is that most of the folks who have more kids will give rise to a generation of have-nots, and they will be on the unhappy side of an ever-wide

The simple answer is that most of the folks who have more kids will give rise to a generation of have-nots, and they will be on the unhappy side of an ever-widening gap between the super educated elites, and the merely educate plebes. It's silly to think that people in the states can simply drop their standards to that of their grandparents, when most of the "grandparent generation" of boomers grew up before most manufacturing jobs were either outsourced or automated. The mass automation of white collar industry that will happen withinin 20 years might reverse the dynamic IMO... where industries with ample training data for AI (mostly white collar knowledge economy stuff) will begin to automate as well, and blue collar jobs like construction (which may take longer to automate) will take much longer.