People live longer than ever before. This, as I noted recently, has created both opportunities and challenges. But postponing death is only a part of the demographic story. The other is the decline in births. The combination of the two is creating huge changes in the world we inhabit.
The notion of a “demographic transition” is almost a century old. Human societies used to have roughly stable populations, with high mortality matched by high fertility. In England and Wales in the 18th and 19th centuries, death rates plummeted. But fertility did not. The result was a population explosion, until, at last, fertility rates also collapsed.
As the benefits of economic growth and advances in medicine and public health spread, most of the world has followed a similar transition, but far faster. As a result, human numbers rose fourfold over the last hundred years, from 2bn to 8bn. In time, however, fertility followed mortality. The result has been plummeting fertility rates (births per woman) across most of the world. According to a study recently published in The Lancet, “Fertility is declining globally, with rates in more than half of all countries and territories in 2021 below replacement level.” For the world as a whole, the fertility rate was 2.3 in 2021, barely above replacement, down from 4.7 in 1960. For high-income countries the fertility rate was a mere 1.6, down from 3 in 1960. In general, poor countries still have higher fertility rates than richer ones, but they have been falling there, too. (See charts.)