The people of first world countries....are limiting their birth of children.
THE TURD WORLD PEOPLE ARE LIKE RABBITS AND MULTIPLY...without thinking if they can feed them. Take care of them.
As harsh as it sounds, that model would work to produce stable numbers if first world countries didn't feed them. Between hunger, disease, and violence, there would be sufficient attrition to reduce the number of children who survived to adulthood, and the number of adults who lived to old age.
It is what they have always done to offset infant and childhood mortality.
Besides, having a large 'tribe' means more warriors who can take what they need.