Most countries conducted their national censuses last year, and the data suggest that fertility rates are plunging in most of them. Birthrates have been low in developed countries for some time, but now they are falling rapidly in the majority of developing countries. The 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. The population may keep growing until midcentury, owing to rising longevity, but, reproductively speaking, our species probably won't be expanding.
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 that rate is at the replacement rate, which is a little above 2.3 for the world as a whole, and somewhat lower, 2.1, for developed countries, reflecting their lower infant-mortality rates.
The total fertility rate for most developed countries now stands well below replacement levels. The average among members of the Organization for Economic Cooperation and Development is around 1.74, but some countries, including Germany and Japan, produce less than 1.4 children per woman.
However, the biggest total fertility declines in recent years have been in developing countries. The rate in China and India was 6.1 and 5.9, respectively, in 1950. It now stands at 1.8 in China, owing to the aggressive one-child policy, while rapid urbanization and changing social attitudes have brought India's down to 2.6.
Not enough girls
Another factor could depress future birthrates in China and India. The Chinese census suggests that there are 118.6 boys being born for every 100 girls, compared with a natural ratio of 105 boys per 100 girls. India has a gender ratio at birth of around 110 boys for every 100 girls. The deviations, usually attributed to a cultural preference for boys, will take an additional toll on both populations.
Indeed, after adjusting for the gender imbalance, China's effective fertility rate is around 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 effective fertility rate stands around 2.4 for the world as a whole, barely above the replacement rate.
Current trends suggest the human race will no longer be replacing itself by the early 2020s. Population growth after this will be caused mostly by people living longer, a factor that will diminish in significance from midcentury.
These shifts have important implications for the global labor supply. China is aging very rapidly, and its working-age population will begin to shrink within a few years. Relaxing the one-child policy might have some positive impact in the very long run, but China is already past the tipping point, pushed there by the combined effect of gender imbalance and a very skewed age structure.
The number of women of childbearing age (15 to 49 years) in China will drop 8 percent between 2010 and 2020, another 10 percent in the 2020s, and, if not corrected, at an even faster pace thereafter. Thus, China will have to withdraw an increasing proportion of its female workforce and deploy it for reproduction and child care. Even if China can engineer this, it implies an immediate outflow from the workforce, with the benefits lagging by 25 years.
Meanwhile, the labor force has peaked or is close to peaking in most major economies. Germany, Japan, and Russia already have declining workforces. The United States is one of a handful of advanced countries with a growing workforce, owing to its relative openness to immigration. But this may change as the source countries become richer and undergo rapid declines in birthrates. Thus, many developed countries will have to consider how to keep people working productively well into their seventies.
India, the only large economy whose workforce will grow in sufficient scale over the next three decades, may partly balance the declines expected in other major economies. But, with birthrates declining there, too, current trends suggest that its population will probably stabilize at 1.55 billion in the early 2050s, a full decade ahead of - and 170 million people below - the U.N. forecast.
Given this, it is likely that world population will peak at nine billion in the 2050s, a half-century sooner than generally anticipated, followed by 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.
Sanjeev Sanyal is Deutsche Bank's global strategist. This was distributed by Project Syndicate.