By Pierre Buhler - New York Times
PARIS — Slow but steady contraction in the north, vigorous and sustained expansion in Africa; seven billion of us by October this year, eight billion sometime around 2025. The latest United Nations population figures provide a dramatic glimpse of how the demographic map of the planet is being reshaped.
For the latest revision of its biennial “World Population Prospects,” the U.N. Population Division has extended its forecasts by 50 years, to 2100. Long-term forecasts must be taken with a grain of salt — they “have no operational role,” as the French demographer Hervé Le Bras has written; they just help “staging and exaggerating today’s fears.”
Still, the margins of error allow for a fairly reliable picture of the world’s population in the decades to come. And what matters more is the breakdown of the aggregate figures, as their distribution holds far-reaching consequences.
For this, demography delivers a high level of certainty. The women liable to give birth within a generation are already born; life expectancy and mortality indexes evolve slowly. The most volatile factor is actually the fertility rate — the number of children per woman. Only if this rate is above the generation replacement level of 2.1 will there be a natural increase of a population. When it hovers between 5 and 7, as it does in some 20 countries, the “compounded interest” effect is extremely powerful.
Unsurprisingly, Asia remains the largest human reservoir, holding more than 60 percent of the world’s population — a proportion that should still be around 55 percent by 2050.
What is most striking, though, is the unabated demographic swelling of Africa. Africa’s population has almost doubled between 1975 and 2000, growing from 416 to 811 million; it will add another 75 percent to reach 1.4 billion people in 2025, and presumably another 55 percent to reach the staggering figure of 2.2 billion by mid-century.
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Pierre Buhler is a former French diplomat and associate professor at Sciences Po, Paris.