What demographers call the Total Fertility Rate is the average number of live births per woman over her lifetime. In the long run, a population is said to be stable if the TFR is at the replacement rate, which is a little above 2.3 for the world as a whole, and somewhat lower, at 2.1, for developed countries, reflecting their lower infant-mortality rates.
The TFR for most developed countries now stands well below replacement levels. The OECD average is at around 1.74, but some countries, including Germany and Japan, produce less than 1.4 children per woman. However, the biggest TFR declines in recent years have been in developing countries. The TFR in China and India was 6.1 and 5.9, respectively, in 1950. It now stands at 1.8 in China, owing to the authorities’ aggressive one-child policy, while rapid urbanization and changing social attitudes have brought down India’s TFR to 2.6.
…. it is likely that world population will peak at nine billion in the 2050’s, a half-century sooner than generally anticipated, followed a sharp decline. One could argue that this is a good thing, in view of the planet’s limited carrying capacity. But, when demographic dynamics turn, the world will have to confront a different set of problems.