In 1968, Paul and Anne Ehrlich published The Population Bomb into a world that had good reason to be frightened by population growth. The number of people alive had doubled in less than fifty years, the annual growth rate was near its historical peak, and the book opened by declaring that the struggle to feed humanity had already been lost.
One world, unevenly inhabited In this 2018 cartogram, each square represents half a million people. The demographic turn does not arrive everywhere at once: countries still growing and countries already below replacement share the same world. Max Roser and Our World in Data, via Wikimedia Commons
The population kept growing. The explosion did not.
The United Nations now projects that world population will peak during this century. More than half of countries and areas are already below replacement fertility, while a smaller group—concentrated in sub-Saharan Africa—will supply much of the growth that remains. The world has not moved neatly from growth to decline. It has entered a long overlap in which old momentum and new fertility patterns point in different directions.
That reversal is the subject of this chapter. It begins with the inherited fear of too many people, follows the demographic transition across regions, and ends with the slow arithmetic through which smaller families become smaller generations. The history is not a victory lap over failed forecasts. Falling child mortality, longer lives, greater agency, and an expanded food supply were real achievements. They also changed the population problem itself.
By the end, the question will have changed. We will know how mortality fell, fertility followed, and age structure hid the reversal for a time. The next chapter then asks why fertility kept falling after mortality and birth rates had both moved much lower.
Citations
- United Nations, Department of Economic and Social Affairs, Population Division, World Population Prospects 2024: Summary of Results, 2024.
- Paul R. Ehrlich and Anne H. Ehrlich, The Population Bomb (Ballantine Books, 1968).