THOMAS MALTHUS first published his “Essay on the Principle of Population”, in which he forecast that population growth would outstrip the world’s food supply, in 1798. His timing was unfortunate, for something started happening around then which made nonsense of his ideas. As industrialisation swept through what is now the developed world, fertility fell sharply, first in France, then in Britain, then throughout Europe and America. When people got richer, families got smaller; and as families got smaller, people got richer.


Now, something similar is happening in developing countries. Fertility is falling and families are shrinking in places— such as Brazil, Indonesia, and even parts of India—that people think of as teeming with children. As our briefing shows, the fertility rate of half the world is now 2.1 or less—the magic number that is consistent with a stable population and is usually called “the replacement rate of fertility”. Sometime between 2020 and 2050 the world’s fertility rate will fall below the global replacement rate.

At a time when Malthusian worries are resurgent and people fear the consequences for an overcrowded planet, the decline in fertility is surprising and somewhat reassuring. It means that worries about a population explosion are themselves being exploded—and it carries a lesson about how to solve the problems of climate change.