For most of human history, the world’s population grew so slowly that for most people alive, it would have felt static. Between the year 1 and 1700, the human population went from about 200 million to about 600 million; by 1800, it had barely hit one billion. Then, the population exploded, first in the United Kingdom and the United States, next in much of the rest of Europe, and eventually in Asia. By the late 1920s, it had hit two billion. It reached three billion around 1960 and then four billion around 1975. It has nearly doubled since then. There are now some 7.6 billion people living on the planet.
Just as much of the world has come to see rapid population growth as normal and expected, the trends are shifting again, this time into reverse. Most parts of the world are witnessing sharp and sudden contractions in either birthrates or absolute population. The only thing preventing the population in many countries from shrinking more quickly is that death rates are also falling, because people everywhere are living longer. These oscillations are not easy for any society to manage. “Rapid population acceleration and deceleration send shockwaves around the world wherever they occur and have shaped history in ways that are rarely appreciated,” the demographer Paul Morland writes in The Human Tide, his new history of demographics. Morland does not quite believe that “demography is destiny,” as the old adage mistakenly attributed to the French philosopher Auguste Comte would have it. Nor do Darrell Bricker and John Ibbitson, the authors of Empty Planet, a new book on the rapidly shifting demographics of the twenty-first century. But demographics are clearly part of destiny. If their role first in the rise of the West and now in the rise of the rest has been underappreciated, the potential consequences of plateauing and then shrinking populations in the decades ahead are almost wholly ignored.