The End of Population Growth

NEW DELHI – According to the United Nations’ Population Division, the world’s human population hit seven billion on October 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 world population will rise to 9.3 billion in 2050 and surpass 10 billion by the end of this century.

Such forecasts, however, 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 suggest 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 may 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 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.