According to the UN’s Population Division, the world’s population hit 7 billion on Oct. 31. As always happens whenever we approach such a milestone, this one has produced a spike in conferences, seminars and learned articles, including the usual dire Malthusian predictions. After all, the UN forecasts that the world population will rise to 9.3 billion in 2050 and surpass 10 billion by the end of this century.
However, such forecasts misrepresent underlying demographic dynamics. The future we face is not one of too much population growth, but too little.
Most countries conducted their national population census last year and the data suggests that fertility rates are plunging in most of them. Birth rates have been low in developed countries for some time, but now they are falling rapidly in the majority of developing countries.
Chinese, Russians and Brazilians are no longer replacing themselves, while Indians are having far fewer children. Indeed, global fertility will fall to the replacement rate in a little more than a decade. Population might keep growing until mid-century, owing to rising longevity, but reproductively speaking, our species should no longer be expanding.
What demographers call the Total Fertility Rate (TFR) 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 Organisation for Economic Co--operation and Development average is at about 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.
An additional factor could depress future birth rates in China and India. The Chinese census suggests that there are 118.6 boys being born for every 100 girls. Similarly, India has a gender ratio at birth of about 110 boys for every 100 girls, with large regional variations. Compare this with the natural ratio of 105 boys per 100 girls.
The deviation is usually attributed to a cultural preference for boys, which will take an additional toll on both populations, as the future scarcity of women implies that both countries’ effective reproductive capacity is below what is suggested by the unadjusted TFR.
Indeed, after adjusting for the gender imbalance, China’s Effective Fertility Rate (EFR) is about 1.5 and India’s is 2.45. In other words, the Chinese are very far from replacing themselves and the Indians are only slightly above the replacement rate.
The EFR stands at about 2.4 for the world as a whole, barely above the replacement rate. Current trends suggest that the human race will no longer be replacing itself by the early 2020s. Population growth after this will be mostly caused by people living longer, a factor that will diminish in significance from mid-century.