that's an important (yet debatable) prediction. historically, in subsistence based economies where more farmhands=more food I think that's been true. and holds true up to the point where costs of living don't exceed net household wages (picture Dickens era chimney sweep kids laboring for a pittance).
what's interesting is that it's not true AT ALL for any other species in nature, only humans in the post ~1800s era have developed a seeming unlimited capability to secure more food for their young. wild deer populations naturally reduce themselves when food is scarce, but humans found a cheat code to growing forever.
hard to say. but it's worth mentioning that although the doubling time for population has been contracting since 1800, it now appears to have flattened and is reversing direction.
maybe more accurate to compare say, fewer people choosing to have children vs fewer kids surviving to adulthood and what conditions contribute more to each
bingo. to those accustomed to a lifetime of privilege, equality feels like oppression.