Billions and Billions


Sometime on October 31st, the world’s population will hit seven billion. The baby who does the trick will most likely appear in India, where the number of births per minute—fifty-one—is higher than in any other nation. But he or she could also be born in China—the world’s most populous country—or in a fast-growing nation like Nigeria or Guatemala or, really, anywhere. The idea that a particular child will on a particular day bring the global population to a particular number is, of course, a fiction; nobody can say, within tens of millions, how many people there are on earth at any given time. The United Nations Population Fund has picked October 31st as its best estimate. That this date is Halloween is presumably just a coincidence.

Depending on how you look at things, it has taken humanity a long time to reach this landmark, or practically no time at all. Around ten thousand years ago, there were maybe five million people on earth. By the time of the First Dynasty in Egypt, the number was up to about fifteen million, and by the time of the birth of Christ it had climbed to somewhere in the vicinity of two hundred million. Global population finally reached a billion around 1800, just a couple of years after Thomas Malthus published his famous essay warning that human numbers would always be held in check by war, pestilence, or “inevitable famine.”

In a distinctly un-Malthusian fashion, population then took off. It hit two billion in the nineteen-twenties, and was three billion by 1960. In 1968, when Paul Ehrlich published “The Population Bomb,” predicting the imminent deaths of hundreds of millions of people from starvation, it stood at around three and a half billion; since then, it has been growing at the rate of a billion people every twelve or thirteen years. According to the United Nations, it reached six billion on October 12, 1999. (A baby boy born in Sarajevo, Adnan Mević, was, for symbolic purposes, designated the world’s six-billionth person and greeted at the hospital by U.N. Secretary General Kofi Annan.) For large and slow-to-reproduce mammals like humans, such a growth curve is, to put it mildly, unusual. Edward O. Wilson has called “the pattern of human population growth” in the twentieth century “more bacterial than primate.”

Predicting where the numbers will go from here is, at least in the short term, pretty straightforward. Fourteen years from now, there will be eight billion people on the planet. At around the same time, India will overtake China as the most populous nation on earth. Most of the growth will occur in the world’s poorer countries. Proportionally, Europe’s population will decline, while Africa’s will increase.

The further ahead you look, the trickier things become. This is partly a matter of birth rates; because the base is now so large, even relatively trivial changes produce enormous effects. In most European nations, and also in countries like Japan and China, birth rates have already fallen below replacement levels. Until quite recently, the U.N. was projecting that rates in other parts of the globe would follow a similar downward slope, so that sometime toward 2050 global population would level out at around nine billion. A few months ago, though, the U.N. announced that it was revising its long-term forecast. The agency now estimates that the number of people on earth in 2100 will be ten billion and still climbing. One reason for the upward revision is that birth rates in many developing countries, particularly in Africa, have remained unexpectedly high. Another is an uptick in births in wealthier countries, like the United States and Britain. (Last week, the Pew Research Center released a report showing that birth rates in the U.S. dipped during the recession that started in 2007; it is doubtful, though, that this will have much impact on long-term population estimates.) If families have, on average, just half a child more than the U.N. currently projects, by 2100 there will be sixteen billion people on the planet. Read more…

As published in The New Yorker (October 24th Print Edition).


Joseph Ting March 16, 2012 - 3:59 am

Read: David Brooks, The Fertility Implosion, Opinion New York Times Mar 12, 2012

and my response to Brooks…

David Brooks contends the declining impetus to have children jeopardizes human prosperity and societal well-being. I agree that the dilemma lies in matching the subsidized needs of a burgeoning number of retirees and the long living elderly (the demand) with children raised to tax-paying independence (the supply). However, this co-dependency holds potential to generate an accelerating demand-supply loop. Today’s children will grow old and in turn seek their due from generations raised to adult productivity that come after them. The cost of raising a child to independence, an increasingly deferred milestone, is not just met by the parents and families but also the rest of society. The demands of bringing up a child would need to be deducted from the potential tax revenue gained from a life time of work to determine whether Brook’s exhortation to reproduce leads to net benefits for retirees, the aged and the infirm.

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