Last week the United Nations Population Fund released a report heralding the birth of the world’s 7 billionth person. The milestone is important, the United Nations explains, because their calculations now project that global population is likely to hit 9.3 billion by 2050 and could go as high as 15.8 billion by the end of the century. As you might imagine, these dire warnings were greeted with eager and solicitous concern by the alarmist media.

“Population Growth Taxing Planet’s Resources,” announced one Washington Post story. CNN tried to contextualize the number 7 billion by helpfully informing readers, “Seven billion ants, at an average size of 3 milligrams each, would weigh at least 23 tons (46,297 pounds).” Why a pretend pile of insects? “Population experts are hoping that more people begin to grasp the 7 billion concept soon, because the number has skyrocketed in recent years and the situation is becoming more urgent.” The New York Times carried a debate on overpopulation in which the Population Institute’s William Ryerson argued that societies with fertility rates below the replacement level—which is to say every industrialized nation in the world—must not try to increase their fertility because to do so will cause “serious environmental and social problems.”

The nub of these arguments is that the world is overcrowded, and there is not enough water, food, energy, or land to sustain an asymptotically increasing population. Happy to go the full Malthus, MSNBC wheeled out a buffet of essays on the subject. The package featured Paul Ehrlich, who testified that “seven billion people is already facing us with horrendous problems, including almost 1 billion people hungry and contributing greatly to the chances of catastrophic climate disruption.” He warned that “a global civilization is in peril” and argued that all governments should adopt the slogan “patriotic citizens stop at two children” while imposing penalties on “over-reproducers and those unethical elements in society that are pro-natalist.”

Following Ehrlich was a piece by actress Alexandra Paul, who argued that Ehrlich’s “only have two” plan—which would merely hold population constant—was madness. She insisted that “we must work to lower the world population to 2 billion.” Meaning that of every ten people alive today, she wants seven scrubbed from the face of the earth.

Ehrlich’s intellectual authority stems from a book he wrote in 1968 which claimed that overpopulation would kill “hundreds of millions” of people in a matter of months. Paul’s derives from the fact she once played a lifeguard with skin cancer on a Very Special Episode of Baywatch. It is difficult to say which is the bigger fool.

Then again, foolishness envelops nearly every popular discussion of demographics these days.

To understand what 7 billion people means, it’s useful to have a sense of population history. It took nearly 500,000 years for the world’s population to hit 5 million, which it did some time around 8,000 b.c. Human life was plenty nasty and brutish back then, but it was the shortness that mattered most. The reason it took so long to get to 5 million was that it was devilishly hard to keep 5 million people alive all at once. But the advent of agriculture improved access to food, which produced gains in health and longevity, which led to a pickup in the rate of population growth: From 8,000 b.c. to the age of Julius Caesar (45 b.c., give or take) the world’s population grew to somewhere in the neighborhood of 300 million.

That growth rate continued more or less from Caesar, through the Middle Ages, until about 1750—bringing the total number of people on our little blue ball of mud to 800 million. But with the 18th century, the pace began to pick up again. This time by a lot. We crossed the threshold of 1 billion around 1825. And while it took thousands of years to get a billion people alive at the same time, it only took another 100 years to get to 2 billion, which is where we stood in 1925. The third billion was added even faster: We hit that milestone in 1960 and have been off to the races ever since.

But the post-1750 population explosion was not caused by more babies being born. It was the result of declining mortality. As nutrition, sanitation, and medicine improved, people began living longer. In ancient Rome, life expectancy was about 25 years. In 19th-century England it was 40 years—an increase of barely 60 percent over the course of 2,000 years. Since then, the average life expectancy in the first world has just about doubled in less than two centuries. As demographers Nathan Keyfitz and Wilhelm Flieger once sardonically noted, the explosion in population after 1750 was “due to death control’s exceeding birth control.” Or, as Nicholas Eberstadt put it, people didn’t suddenly start breeding like rabbits; they stopped dying like flies.

The decline in mortality created what is known as demographic momentum, as entire generations remained in the ranks of the living where they once would have quickly passed away. Seen in this light, complaints about overpopulation are really complaints that people now grow old before dying.

But no one wants to send Grandpa to the wolves, and besides, people like Paul Ehrlich and Alexandra Paul seem to enjoy living, even if it means a slow descent into decrepitude. So instead of admitting that the “problem” is people living too long, they claim that we’re all in trouble because people are having too many babies. Only they’re wrong about that, too.

The collapse of the death rate was in fact followed by a collapse of the fertility rate. Around the time of the industrial revolution, women began bearing steadily fewer children. In America, for instance, the average white woman had 7.04 children in 1800. By 1944, that number had eased to 2.22. This gradual decline became an absolute collapse once the Baby Boom ended. Since 1970, the fertility rate has dropped by more than 50 percent in nearly every country in the world. In many countries the decline has been closer to 75 percent. In some countries fertility rates have reached “lowest-low”—which is to say, lower than has ever been seen in human history. Today, no first-world country has a fertility rate above the replacement level of 2.1. Most developing countries are still above that mark, but are falling, fast.

Which means that, while total population keeps increasing, the rate of increase has slowed dramatically. Seven billion people may seem like a lot, but what the U.N. isn’t advertising is that over the last few decades population growth has consistently lagged behind projections. The U.N.’s 1994 model, for instance, had us hitting the 7 billion mark nearly three years ago. The real story of the 7 billionth birth is that fertility rates have fallen so far that population has been growing much more slowly than anyone predicted. And, as a corollary, this sluggish growth is likely to disappear as global population peaks, and then begins contracting.

Indeed, nearly every population model in recent years has suggested that, between 2050 and 2075, world population will top out at 9 billion to 12 billion. And after that it will begin shrinking.

Until a few months ago, the U.N.’s model predicted pretty much the same thing. But when the United Nations Population Division released its 2010 revision, it changed course. It now projects that population decline probably won’t materialize in the next 90 years. Instead, the new model suggests that world population will keep growing all the way through 2100. And once the U.N. Population Fund—that’s the political action arm to the Population Division’s research shop—got hold of these numbers, it rushed to publicize them. Thus the creation of the 7 billionth birth media sensation, which the Population Fund “symbolically” scheduled for October 31. (They are as obvious as they are earnest.)

The symbolic date is worth mentioning because the Population Fund admits it actually has very little idea when the 7 billionth person will be (or was) born. They believe their calculations have a 1 percent margin of error—which means that the birth could have happened six months ago. Or might not happen for another six months. But never mind; to go with their pretend day, they anointed a little girl born in the Philippines as the pretend 7 billionth baby. The Population Fund loves symbolism so much that this little girl was only the first of several “symbolic” 7 billionth babies it recognized across the globe.

All of which is worth keeping in mind when you consider the methodology of the U.N.’s latest population projection. In order to upend decades of data projecting world population contraction, the U.N. had to assume that over the next 70 years, in every part of the world where the fertility rate is now below 2.1, fertility will steadily increase to the replacement level. Starting tomorrow. The model supposes this for countries both big and small, secular and religious, with massive amounts of immigration and with no immigration. It assumes this amazing reversal even for countries such as Poland, which is working on 60 consecutive years of declining fertility.

How did the demographers at Turtle Bay come up with such a counter-intuitive prediction? They looked at a handful of countries—mostly in Scandinavia—which had low fertility rates in the 1930s, but have somewhat recovered today. They then assumed that the rest of the world—Italy, Singapore, China, Iran, Costa Rica, Russia—will follow the same fertility path as Sweden.

Now, who knows, maybe this assumption—however improbable—will prove correct. But it seems more likely that, like most of the population projections of the last 40 years, it will overshoot the mark. Not that the overpopulation hysterics will notice. The 8 billionth birth is just around the symbolic corner.

Jonathan V. Last is a senior writer at The Weekly Standard.

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