Demographics is fun. It is a subject with lots of data and pretty good mathematical models, and hardly anyone bothers to check either, or compare them against one another. John was careful not to give population models too much credence, he knew how often reality conspired to overturn the modeler's assumptions.
I was actually just finishing my review of Pat Buchanan's The Death of the West when I saw the story from Reuters. (Links are to the left; I prefer not to imbed them.) As you know, The Death of the West argues that the very existence of Western countries is in peril because their fertility rates are below those needed to maintain their populations. Now the Centers for Disease Control & Prevention say that is no longer true with regard to the United States. This development is actually just a return to replacement levels, but you may have already seen the expression "new babyboom" in a few places. Probably you will see quite a lot of it by mid-summer.
Demographic history is not one of my chief interests, but I do know enough about it to realize that it is one of those "everything you know is a lie" subjects. For instance, those nice, smooth, population-growth curves that you see in books by people like Paul Ehrlich are wildly misleading. The population of France, for instance, expanded into the fourteenth century, crashed with the plague, and then oscillated between 12 million and 20 million before beginning a steady rise in the late 17th century. Pretty much the same thing happened in China at pretty much the same time.
The world's population jumps from plateau to plateau and then takes a rest. The world's major population centers have always been more or less in sync. It is sometimes said that you have to go back to Roman times to find anything like today's low growth rates for Western Europe. True enough: the phenomenon started in the late Republic, though it never applied to the east under the Empire. In any case, much the same seems to have been true of Han China; Turkic peoples overran the depopulated north of China at about the time the Germans were overrunning the late Roman Empire.
We are still in sync, on the scale of a hundred years or so. In the unlikely event that present trends continue, the population of China will increase from 1.3 billion now to 1.5 billion in 2050, and then stabilize or decline. There are places in the world with explosive fertility rates, notably the Middle East and Africa; low child-mortality is still new there. Even moderately developed countries tend to fall to replacement level. Brazil and Thailand are in that range. So is Mexico; all that emigration comes from slow economic growth, not population pressure.
Today there are about 280-million people in the United States. In 1900, there were about 75 million. However, it was in the earlier year that people were more crowded. Even though most people still lived in rural areas, they had less living space in their houses. Cities, of course, were rabbit warrens. Only as population increased did economies of scale make it feasible to build more ample housing and move it out to the suburbs. If there were a billion people in the United States, most of the country, like China today, would still be wilderness. Conversely, as we see in Siberia and parts of the American Midwest today, declining population means that roads are not repaired and public institutions are closed. People have to move closer to the remaining schools and hospitals, not to mention to such jobs as remain in a world of declining demand. Taxes rise per capita. Even solitude becomes less possible as the growing wilderness becomes less accessible.
This is not what the Zero Population Growth advocates want, but it is the future they have actually been working for.