As birth announcements go, it was momentous. On November 24th India’s government declared that the country’s fertility rate had dropped to 2.0 children per woman. That is below the replacement rate—at which new births are sufficient to maintain a steady population—and puts India in the company of many richer economies. Indeed, fertility rates are now below replacement level in all four “ bric” countries (Brazil, Russia, India and China), with the population probably falling in Russia and China. It is no surprise that emerging economies should follow a demographic trajectory similar to that travelled by rich economies before them. But the pace of change seems to be accelerating, with potentially profound implications for the global economy.

What social scientists refer to as the “demographic transition” has long been an essential feature of economic modernisation. In pre-industrial societies both birth and death rates (annual births and deaths per 1,000 people) were very high, and overall population growth was uneven and slow. But in the 18th century, death rates in parts of north-west Europe began to decline, marking the first stage of a seismic demographic shift. Falling death rates led to rapid population growth; Britain’s population roughly doubled between 1760 and 1830. Yet from the late 18th century, fertility rates began to decline as well. By the 20th century, birth and death rates in rich countries stabilised at low levels, leading to slow or even negative population growth in the absence of immigration.

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