Low birthrates aren't the result of economic growth and political stability; they're a prerequisite.
There is a well-known story about how a society stabilizes its population. As a country transitions from poverty to affluence, birthrates plunge—from six or eight children per woman to just about two. Population growth levels off. Prosperity and education, the story goes, are just about the best form of birth control there is. But this tale gets it backward. Low birthrates aren’t a consequence of national wealth; rather, they’re needed to create it. Soaring unemployment, endemic poverty, and flailing schools are quite simply impossible to combat when every year adds more and more people.