Turns out fertility rates have been falling all by themselves. Any rate below 2.1 means a population isn't even replacing itself, and America's rate is already down to 1.99. But world-wide, that's down from an average of 5 children per woman as recently as the early 1950s. But that will have a far smaller impact than the tripling of the world population from 1927 to 1999. And at that point, it actually appears human population could start to fall .
People think it's out of control, that the population is growing like cancer.
People are controlling their own lives and this has impacts on the number of children we have. We have virtually no country anymore that has not started at least a modest fertility decline. How about that.