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Peak Population?
"A MAN YOUR AGE WITH NO CHILDREN?" blurted out my flabbergasted Johannesburg taxi driver. I was then forty-eight years old and taking a long cab ride from Sandton, where the UN's 2002 World Summit on Sustainable Development had convened, to a Soweto township venue in South Africa. As is my usual practice, I had gotten into the front seat to make conversation.
After we'd gone through the preliminaries about what had brought me to Johannesburg, my very hospitable driver, who looked to be in his fifties, asked me if I was married. "Yes," I replied. "How many children do you have?" he amiably asked. "None," I replied. My driver nearly veered off the road in shock. "Are there problems?" he carefully inquired. "No," I replied, "my wife and I decided not to have children." "Who is going to support you in your old age?" he wondered. I elected not to try to explain to him about retirement funds and Social Security and instead turned the questions around, asking him, "Well, how many children do you have?"
"Six," he replied with evident satisfaction. "Why so many?" I asked. "Because two of them are going to be rotters and just leave you," he genially explained. "Two others will support you when you get old. And you need two younger ones at home to fetch you beers from the fridge after work."
"How many children did your father have?" I asked. "I am one of twelve," my driver replied, adding that he had grown up on a farm in the northern part of the country. Then I asked, "How many children do your kids have now? "None," he replied with a hint of a frown. "City life is so expensive, a couple are still finishing up school, and good jobs are hard to find," he explained.
That's the demographic transition right there, I thought to myself.
Population researchers define the demographic transition as the change in the human condition from high mortality and high fertility to low mortality and low fertility. Initially, both birthrates and death rates are high and natural population growth is low. With the advent of modern medicine and sanitation, mortality rates fall and fertility remains high, producing a rapidly growing population. Eventually fertility rates also fall, leading to a reduction in the rate of population growth. "Population increases not because people start breeding like rabbits, but because they stop dying like flies," explains American Enterprise Institute demographer Nicholas Eberstadt.
In premodern societies, average life expectancy was under forty years, nearly a third of children died before reaching age five, child labor was vital to mostly rural families, and few women had access to education or contraception. Global average life expectancy is now over seventy years, only one in twenty children die before their fifth birthdays, urbanized child-rearing is costly, and many more women are educated and have access to contraception.
As a result of these trends, women in 1970 globally averaged 4.7 children over the courses of their lives, and that has fallen to 2.45 children in 2013. A population becomes stable when as many people are born as die. This occurs when the total fertility rate is approximately 2.1 children per woman; the extra tenth of a child takes into account pre-reproduction deaths, infertility, and people like my wife and me who choose not to have children.
Leading demographers expect that as the twenty-first century unfolds, women across the globe will be giving birth to fewer and fewer children. The upshot will be slowing population growth and eventually a reversal of trend in which world population begins to shrink. According to a long line of environmentalist doomsayers, this was not supposed to happen.
The Population Bomb
"The battle to feed all of humanity is over. In the 1970s the world will undergo famines-hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now," predicted Stanford University biologist Paul Ehrlich in his 1968 bestseller, The Population Bomb. Ehrlich was not a lone voice proclaiming the advent of imminent massive famines. A year earlier in their bestselling book, Famine 1975! America's Decision: Who Will Survive?, William and Paul Paddock warned, "By 1975 a disaster of unprecedented magnitude will face the world. Famines, greater than any in history, will ravage the undeveloped nations. A swelling population is blotting up the earth's food." They confidently added, "Our technology will be unable to increase food production in time to avert the deaths of tens of millions people by starvation."
In his famous 1968 essay "The Tragedy of the Commons," published in the journal Science, ecologist Garrett Hardin flatly declared, "The freedom to breed is intolerable." To illustrate the harms of the freedom to breed, he conjures up the arresting example of a pasture open to all people in a village. Each herdsman, seeking to maximize his individual gain, puts as many cattle on the pasture as possible, leading eventually to its destruction from overgrazing. "Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons," wrote Hardin. "Freedom in a commons brings ruin to us all." According to Hardin, ceaselessly breeding human beings treat the Earth like a village commons and would soon "overgraze" the planet. Hardin thus concluded that "the inherent logic of the commons remorselessly generates tragedy."
Another prominent prognosticator of population doom is Lester Brown, the founder of the Worldwatch Institute and the Earth Policy Institute. Back in 1963, when Brown was a young bureaucrat in the US Department of Agriculture, he declared, "The food problem emerging in the less-developing regions may be one of the most nearly insoluble problems facing man over the next few decades." In 1967, Brown explained, "As the non-recurring sources of [agricultural] productivity are exhausted ... the rate of increase in yield per acre begins to slow." In 1974, Brown maintained that farmers "can no longer keep up with rising demand; thus the outlook is for chronic scarcities and rising prices." In 1989, Brown stated that "global food insecurity is increasing," and further claimed that "the slim excess of growth in food production over population is narrowing." Brown contended that "population growth is exceeding the farmer's ability to keep up," concluding that "our oldest enemy, hunger, is again at the door." In 1995, Brown starkly warned, "Humanity's greatest challenge may soon be just making it to the next harvest." In 1996, Brown again proclaimed, "Food scarcity will be the defining issue of the new era now unfolding." In a 2012 Scientific American article, Brown asked, "Could food shortages bring down civilization?" Not surprisingly, Brown's answer was an emphatic yes. Given his past record, he astonishingly claimed that for years he has "resisted the idea that food shortages could bring down not only individual governments but also our global civilization." Now, however, Brown said, "I can no longer ignore that risk." Also in 2013, Brown once again declared, "The world is in transition from an era of food abundance to one of scarcity."
The population doomsters offered stark plans to handle the impending global famines. The Paddock brothers advised a form of triage, in which the United States would pick countries worthy of food aid and leave tens of millions of people in India, Haiti, and Egypt to starve to death. In The Population Bomb Ehrlich compared humanity to a growing cancer on the Earth. "A cancer is an uncontrolled multiplication of cells; the population explosion is an uncontrolled multiplication of people," wrote Ehrlich. What must be done? "We must shift our efforts from treatment of the symptoms to the cutting out of the cancer. The operation will demand many apparently brutal and heartless decisions." What sorts of heartless decisions? The November 25, 1969, The New York Times reported, "Dr. Paul Ehrlich says the U.S. might have to resort to addition of temporary sterility drugs to food shipped to foreign countries or their water supply with limited distribution of antidote chemicals, perhaps by lottery."
That was then, but what about now?
Though it is tragically true that over the decades tens of millions have died of the effects of malnutrition, the world-spanning massive famines predicted by Ehrlich and the Paddocks did not come to pass. Instead, world population since 1968 has essentially doubled from 3.6 billion to 7.2 billion today. While the overpopulation dirge has become somewhat muted as a result of their massive predictive failure, many of the more radical environmentalist ideologues still sing the same old Malthusian song.
Malthusianism Forever?
Modern promoters of imminent population doom are the intellectual disciples of the eighteenth-century economist Reverend Thomas Robert Malthus. In the notorious first edition of his An Essay on the Principle of Population,Malthus claimed that human numbers would always outrun the amount of food available to feed people. Malthus advanced two propositions that he regarded as completely self-evident. First, that "food is necessary for the existence of man," and second, that "the passion between the sexes is necessary and will remain nearly in its present state." Based on these propositions, Malthus concluded that "the power of population is indefinitely greater than the power in the earth to produce subsistence for man. Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio. A slight acquaintance with numbers will show the immensity of the first power in comparison with the second." In other words, Malthus was arguing that population doubled at an exponential rate of 2, 4, 8, 16, 32, and so forth, whereas food production increased additively, rising one unit at a time, like 2, 3, 4, 5, 6, 7, 8, and so forth. Malthus additionally asserted that "population does invariably increase where there are the means of subsistence." Malthus therefore dismally concluded that some portion of humanity must forever be starving to death.
According to Malthus, there are two kinds of checks on population, preventive and positive. Preventive checks, those that prevent births, include abortion, infanticide, and prostitution; positive checks include war, pestilence, and famine. In later editions of his essay, Malthus added a third check that he called "moral restraint," which includes voluntary celibacy, late marriage, and the like. Moral restraint is basically just a milder version of the earlier preventive check.
If all else failed to keep human numbers under control, Malthus chillingly reckoned:
Famine seems to be the last, the most dreadful resource of nature. The power of population is so superior to the power in the earth to produce subsistence for man, that premature death must in some shape or other visit the human race. The vices of mankind are active and able ministers of depopulation. They are the precursors in the great army of destruction, and often finish the dreadful work themselves. But should they fail in this war of extermination, sickly seasons, epidemics, pestilence, and plague, advance in terrific array, and sweep off their thousands and ten thousands. Should success be still incomplete, gigantic inevitable famine stalks in the rear, and with one mighty blow, levels the population with the food of the world.
Reading Malthus in 1838 was a eureka moment for the founding father of modern biology, Charles Darwin, who declared in his autobiography, "I had at last got a theory by which to work." Darwin realized that Malthus's thesis applied to the natural world, since plants and animals produce far more offspring than there are food, nutrients, and space to support them. Consequently, Darwin noted, "It at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species." This insight formed the basis for one of the most important modern scientific theories, the theory of biological evolution by means of natural selection.
Ever since, biologists have been entranced by the idea that if Malthusianism can explain the operation of the natural world, it should also explain the functioning of human societies. Are we not just complicated animals? Shouldn't this biological insight apply to us, too?
The Neo-Malthusians
The most prominent among the neo-Malthusians is Paul Ehrlich. Despite his utter failure as a prophet, Ehrlich continues to preach that overpopulation is humanity's biggest problem. "The human predicament is driven by overpopulation, overconsumption of natural resources, and the use of unnecessarily environmentally damaging technologies and socio-economic-political arrangements to service Homo sapiens' aggregate consumption," wrote Ehrlich and his wife, Anne, in the March 2013 issue of the Proceedings of the Royal Society B. During a May 2013 conference at the University of Vermont, Ehrlich asked, "What are the chances a collapse of civilization can be avoided?" His answer was 10 percent.
Even now the Ehrlichs are far from alone in propagating forecasts of overpopulation doom. "The world faces a serious overpopulation problem," asserted Cornell University researcher David Pimentel in his 2011 article "World Overpopulation." "The world's biggest problem?" asks a 2011 op-ed by researchers Mary Ellen Harte and Anne Ehrlich in the Los Angeles Times. "Too many people," they answer. "We are a plague upon the earth," declared nature documentarian Sir David Attenborough. "Either we limit our population growth or the natural world will do it for us." Attenborough expressed these dour sentiments in The Telegraph in January 2013.
In his 2013 rant Ten Billion, Microsoft Research computer scientist Stephen Emmott argued that humanity's growing population constitutes "an unprecedented planetary emergency." Emmott asserts, "As the population continues to grow, our problems will increase. And this means that every way we look at it, a planet of ten billion people is likely to be a nightmare." In the somewhat more hopeful 2013 book Countdown: Our Last, Best Hope for a Future on Earth?, journalist Alan Weisman declares that "this will likely be the century that determines what the optimal human population is for our planet." We can choose to limit population growth, argues Weisman, "or nature will do it for us, in the form of famines, thirst, climate chaos, crashing ecosystems, opportunistic disease, and wars over dwindling resources that finally cut us down to size."
More Food Equals More Kids?
In fact, the chief goal of most species is to turn food into offspring: the more food, the more offspring. "To ecologists who study animals, food and population often seem like sides of the same coin," wrote Paul and Anne Ehrlich in 1990. "If too many animals are devouring it, the food supply declines; too little food, the supply of animals declines." They further asserted, "Homo sapiens is no exception to that rule, and at the moment it seems likely that food will be our limiting resource." By limiting, they meant starvation.
Neo-Malthusians like the Ehrlichs, Pimentel, and Emmott cannot let go of the simple but clearly wrong idea that human beings are no different than a herd of deer when it comes to reproduction. For example, in an article called "Human Carrying Capacity Is Determined by Food Availability," in the November 2003 issue of the journalPopulation and Environment, Duke University researcher Russell Hopfenberg wrote: "The problem of human population growth can be feasibly addressed only if it is recognized that increases in the population of the human species, like increases in the population of all other species, is a function of increases in food availability." More food means more kids.
It is true that as food supplies have increased, so have human numbers. But Hopfenberg and other neo-Malthusians are overlooking some crucial data. The countries with the greatest food security are also the countries that are experiencing below replacement fertility. High fertility does not correlate with improved food availability. Consider that of the thirty-four nations that are members of the rich country club the Organisation for Economic Co-operation and Development, only Mexico has an above replacement rate fertility of 2.22 children. All the rest are at or well below the replacement rate. More generally, as food security has increased around the world, instead of increasing as Hopfenberg's neo-Malthusian theory would suggest, global average fertility rates have dropped from around 5 children per woman in 1960 to 2.45 today.
Instead, the highest fertility rates occur in countries where food insecurity is greatest. The International Food Policy Research Institute's 2013 Global Hunger Index takes into account undernourishment rates, percentage of underweight children, and child mortality rates in various countries. Of the nineteen countries where the level of hunger was rated as alarming or extremely alarming, fifteen had total fertility rates higher than 4.5 children per woman. It is notable that Niger's total fertility rate of 7.6 children per woman is the highest in world. As we shall see, demographers have developed persuasive explanations for why people in countries suffering from food insecurity choose to have more children.
So how did humanity avoid the massive famines so confidently predicted by environmentalist millenarians like Ehrlich, Brown, and the Paddocks? Unlike deer that starve when their food runs out, people work to increase supplies. As it turns out, food plants and animals are populations, too, and can be, contrary to Malthus, increased at exponential rates.
Norman Borlaug and the Green Revolution
Norman Borlaug is the man who saved more human lives than anyone else in history. Borlaug was the father of the Green Revolution, the dramatic improvement in agricultural productivity that swept the globe in the 1960s. For spearheading this achievement, he was awarded the Nobel Peace Prize in 1970. One of the great privileges of my life was getting to meet and talk with Borlaug many times. He died in 2009 at age ninety-five.
Borlaug grew up on a small farm in Iowa and graduated from the University of Minnesota, where he studied forestry and plant pathology, in the 1930s. In 1944, the Rockefeller Foundation invited him to work on a project to boost wheat production in Mexico. At that time, Mexico could not feed itself and was importing half of its wheat supplies. Backed by $100,000 in annual funding from the foundation, Borlaug and his colleagues succeeded brilliantly in boosting the productivity of poor Mexican farmers. They did this by breeding new, highly productive dwarf wheat varieties that enabled Mexico to become self-sufficient in grains by 1956. By 1965, Mexican wheat yields had risen 400 percent over their levels in 1950.
In 1952, the Rockefeller Foundation began funding a similar effort to boost the productivity of poor farmers in India. In the mid-1960s, India was importing grains to avert looming famines. The dwarf wheat varieties developed by Borlaug and his colleagues were again decisive in winning the battle against hunger on the subcontinent.
In the late 1960s, as noted earlier, predictions of imminent global famines in which billions would perish were widespread. Recall that chief among the doomsters was The Population Bomb author Paul Ehrlich, who, as we've seen, predicted that in the 1970s "millions of people will starve to death in spite of any crash programs embarked upon now." Ehrlich also declared, "I have yet to meet anyone familiar with the situation who thinks India will be self-sufficient in food by 1971." And he further insisted that "India couldn't possibly feed two hundred million more people by 1980."
As we now know, Borlaug and his team were already engaged in exactly the kind of crash program that Ehrlich declared wouldn't work. Their dwarf wheat varieties resisted a wide spectrum of plant pests and diseases and produced two to three times more grain than the traditional varieties. In 1965, they launched a massive campaign to ship the miracle wheat to Pakistan and India and teach local farmers how to cultivate it properly. Soon after Borlaug's success with wheat, his colleagues at the Consultative Group on International Agricultural Research working at the International Rice Research Institute in the Philippines developed high-yield rice varieties that quickly spread the Green Revolution through most of Asia. By 1968, when Ehrlich's book appeared, the US Agency for International Development was already hailing Borlaug's achievement as a Green Revolution.
Borlaug's achievements were not confined to the laboratory and fields. He insisted that governments pay poor farmers world prices for their grain. At the time, many developing nations-eager to supply cheap food to their urban citizens, who might otherwise rebel-required their farmers to sell into a government concession that paid them less than half of the world market price for their agricultural products. The result, predictably, was hoarding and underproduction. Using his hard-won prestige as a kind of platform, Borlaug persuaded the governments of Pakistan and India to drop such self-defeating policies. Fair prices and high doses of fertilizer combined with new grains changed everything. By 1968 Pakistan was self-sufficient in wheat, and by 1974 India was self-sufficient in all cereals.
Instead of cheering the successes of the Green Revolution, Ehrlich doubled down on his predictions of imminent global collapse. In a 1969 article, "Eco-Catastrophe," in Ramparts magazine, he excoriated people "lacking the expertise to see through the Green Revolution drivel" for failing to realize that by "the early 1970s, the 'Green Revolution' was more talk than substance." Ehrlich derided officials in the US Department of Agriculture and Agency for International Development for supposedly "rav[ing] about the approaching transformation of agriculture in the underdeveloped countries (UDCs)." He continued, "Most historians agree that a combination of utter ignorance of ecology, a desire to justify past errors, and pressure from agroindustry" was behind the Green Revolution propaganda campaign. In his dire scenario, famines would soon break out first in India and Pakistan, but soon spread to "Indonesia, the Philippines, Malawi, the Congo, Egypt, Colombia, Ecuador, Honduras, the Dominican Republic, and Mexico." Ehrlich's prophecy of famine ends by proclaiming, "Everywhere hard realities destroyed the illusion of the Green Revolution."
The famines didn't happen. In Pakistan, wheat yields rose from 4.6 million tons in 1965 to 8.4 million in 1970. In India, wheat yields rose from 12.3 million tons to 20 million. And the yields continue to increase. The US Department of Agriculture is projecting Pakistan's 2014 wheat harvest at 24.5 million tons and India's at a record 96 million tons. Since Ehrlich's dire predictions in 1968, India's population has risen from 500 million to 1.2 billion and its economy has grown tenfold. Concurrently, its wheat production has also increased nearly fivefold. Both Pakistan and India export grain today. India is expected to export 18 million tons of grain in 2014.
Contrary to Ehrlich's bold pronouncements, hundreds of millions didn't die in massive famines. India fed far more than 200 million more people, and by 1971 it was close enough to self-sufficiency in food production that Ehrlich discreetly omitted his prediction about that from later editions of The Population Bomb. The last four decades have seen a "progress explosion" that has handily outmatched any "population explosion."
The Food and Agriculture Organization's global food production index (2004 - 2006 = 100) rose from 36 to 117 between 1961 and 2012. That means that over the past fifty or so years, world food production has more than tripled. In the meantime, world population increased from just over 3 billion in 1961 to 7.1 billion people in 2012, and the amount of food per person increased by about a third. The FAO further reports that between 1961 and 2009 (the latest figures available), global per capita annual consumption of cereals increased from 282 to 327 pounds, vegetables from 140 to 290 pounds, and meat from 51 to 92 pounds.
According to a 2008 World Bank report, as a result of the increase in food supplies, per capita consumption in developing countries rose from an average of 2,100 calories per day in 1970 to almost 2,700 calories today. That report further observes that "the proportion of people suffering from hunger has fallen by half since the 1960s, from more than one in three to one in six, even as [the] world's population has doubled." While progress has been made, some 870 million people are still undernourished.
Occasional local famines in poor countries caused by armed conflicts or political mischief do still occur. But food is more abundant today than ever before in history, due in large part to the work of Borlaug and his colleagues, and no thanks to neo-Malthusian false prophets like Paul Ehrlich and Lester Brown.
Can We Feed the World in 2050?
Looking to the future, what is likely to happen? The International Food Policy Research Institute projects that farmers will have to produce about 70 percent more food than they do today in order to provide the projected population in 2050 with a nutritionally satisfactory diet.
The journal Philosophical Transactions of the Royal Society B (Biological Sciences) devoted its September 27, 2010, issue to analyzing the issue of global food security through 2050. In one of the specially commissioned research articles, it is projected that world population will reach around 9 billion by 2050, and that in the second half of the twenty-first century, "population stabilization and the onset of a decline are likely." Can the world's farmers be reasonably expected to provide enough food for 9 billion people by 2050?
Two other articles in the special Royal Society issue on global food security conclude yes. A review of the relevant scientific literature led by Keith Jaggard from Rothamsted Research looks at the effects of climate change, CO2increases, ozone pollution, higher average temperatures, and other factors on future crop production. Jaggard and his colleagues conclude: "So long as plant breeding efforts are not hampered and modern agricultural technology continues to be available to farmers, it should be possible to produce yield increases that are large enough to meet some of the predictions of world food needs, even without having to devote more land to arable agriculture."
Applying modern agricultural technologies more widely would also go a long way toward boosting yields. In his 1997 article "How Much Land Can Ten Billion People Spare for Nature?," published by the National Academy of Engineering, agronomist Paul Waggoner argued that "if during the next sixty to seventy years the world farmer reaches the average yield of today's U.S. corn grower, the 10 billion will need only half of today's cropland while they eat today's American calories."
University of Minnesota biologist Ronald Phillips points out that India produces 31 bushels of corn per acre now, which is at the same point US yields were in the 1930s. Similarly, South Africa produces 40 bushels (US 1940s yields); Brazil 58 bushels (US 1950s yields); China 85 bushels (US 1960s yields). Today's modern biotech hybrids regularly produce more than 160 bushels of corn per acre in the Midwest. For what it's worth, the corporate agriculture giant Monsanto is aiming to double yields on soybeans and cotton by 2030. Whether or not specific countries will be able to feed themselves has less to do with their population growth than it does with whether they adopt policies that retard their economic growth.
An Overpopulated Nightmare?
Will the twenty-first century be an overpopulated nightmare, as Stephen Emmott asserts? There are good reasons to doubt it. First, let's take a look at the latest population projections by the United Nations. Every two years the United Nations Population Fund issues estimates for future population. In their latest report, World Population Prospects: The 2012 Revision, demographers at the United Nations boosted projected world population numbers by 600 million. The UN experts offer low-variant, middle-variant, high-variant, and constant fertility trends. The new estimates of the middle-variant projections of future population in 2050 increased from 9 billion in the UN's2010 Revision to 9.6 billion and from 10 billion to 10.9 billion by 2100.
The UN's middle-variant projection is generally taken to be the most likely path of future population growth. The difference between the low- and the high-variant projections is basically one child. In the new low-variant projection, world population would reach 8.3 billion by 2050, whereas the high-variant projection would result in a population of 10.9 billion by then. As the report explains, "Thus, a constant difference of only half a child above or below the medium variant would result in a global population in 2050 of around 1.3 billion more or less compared to the medium variant of 9.6 billion."
UN estimates are not universally accepted. Many other demographers believe that the new UN projections are too high. For example, in a 2013 study, Félix-Fernando Muñoz and Julio A. Gonzalo, researchers associated with the Spanish Foundation for Science and Technology, find that past population growth has generally followed the UN's low-variant trend. Using sophisticated statistical techniques, the two calculate that future population growth will most likely continue to track the UN's low-variant trends. "Overpopulation was a spectre in the 1960s and 70s but historically the UN's low fertility variant forecasts have been fulfilled," noted Muñoz. If the Spanish researchers are right, world population will top out at between 8 and 9 billion by mid-century and thereafter begin declining.
In 2001, International Institute for Applied Systems Analysis (IIASA) demographer Wolfgang Lutz and his colleagues published "The End of World Population Growth" in the journal Nature. Lutz and his fellow researchers calculated that "there is around an 85 per cent chance that the world's population will stop growing before the end of the century. There is a 60 per cent probability that the world's population will not exceed 10 billion people before 2100, and around a 15 per cent probability that the world's population at the end of the century will be lower than it is today." In a 2013 study in Demographic Research, the IIASA researchers noted that "most existing world population projections agree that we are likely to see the end of world population growth (with a peak population of between eight and ten billion) during the second half of this century." In another 2013 study for the United Nations, the IIASA demographers project that world population will most likely peak around 2070 at 9.4 billion and fall back below 9 billion by 2100.
In a September 2013 Deutsche Bank report, demographer Sanjeev Sanyal argued that the latest UN population projections are way too high and that world population will likely peak at 8.7 billion around 2050 and then begin falling. Sanyal noted that in recent decades total fertility rates have fallen much more sharply than predicted in countries like China, India, Iran, and Bangladesh. He makes the case that rates are at the brink of similarly steep declines in current high-fertility countries such as Nigeria and Pakistan. As a consequence, Sanyal argues that "the world's overall fertility rate will fall to replacement rate by 2025. In other words, reproductively speaking, our species will no longer be expanding-a major turning point in history." Thus, Sanyal and his colleagues predict, "World population will peak around 2055 at 8.7 billion and will then decline to 8 billion by 2100. In other words, our forecasts suggest that world population will peak at least half a century sooner than the U.N. expects." Basically, Sanyal's analysis agrees with the researchers from the Spanish Foundation for Science and Technology that the trajectory of world population will most likely track the UN's low-variant trend and peak by the middle of this century.
In September 2014, demographers working with the United Nations Population Division published an article inScience arguing that world population stabilization is unlikely in this century. Instead, world population is projected to grow to around 11 billion by 2100. Nearly all of the projected increase-4 billion people-will happen in sub-Saharan Africa. However, the forecast basically assumes that Africa will remain an economic and political hellhole for the remainder of the century. In their November 2014 study, World Population and Human Capital in the Twenty-First Century, Wolfgang Lutz and his fellow demographers at the International Institute for Applied Systems Analysis counter that this prospect is unlikely. The chief difference between the two population forecasts is the issue of the education of women. The analysis done by Lutz and his colleagues takes into account the fact that the education levels of women are rising fast around the world, including in Africa. "In most societies, particularly during the process of demographic transition, women with more education have fewer children, both because they want fewer and because they find better ways to pursue their goals," they note. Given current age, sex, and educational trends, they estimate that world population will most likely peak at 9.6 billion by 2070 and begin falling. If, however, the boosting of educational levels is pursued more aggressively, then world population will instead top out at 8.9 billion in 2060 and begin dropping. Let us turn now to a fuller consideration of the theories and data that underpin the latest projections of global demographic trends.
Liberate Women, Reduce Population
So why is human fertility falling even as food has become generally more plentiful? Demographers, economists, and evolutionary psychologists have all contributed to a vast and ever-growing literature on this subject. All their explanations converge on the notion that as people become wealthier and more educated, they tend to switch from having more children to having fewer healthier and more highly educated children. Demographers call this the quantity-quality trade-off.
Falling fertility rates are overdetermined-that is, there is a plethora of mutually reinforcing data and hypotheses that explain the global downward trend. These include the effects of increased economic opportunities, more education, longer lives, greater liberty, and expanding globalization and trade, among others. The crucial point is that all of these explanations reinforce one another and synergistically accelerate the trend of falling global fertility.
Even more interestingly, all of them emphasize how the opportunities afforded women by modernity produce lower fertility. Let's briefly consider some of the fascinating contemporary research on the underlying causes of the demographic transition and what will likely happen to future human population growth.
First, recent research applying insights from evolutionary biology shows that people are not reproductive automatons driven remorselessly by blind instinct to maximize the number of their offspring, as most other species are. For example, research in 2008 by University of Michigan evolutionary biologist Bobbi Low and her colleagues analyzed the reproductive patterns of women in 170 countries. Their study, "Influences on Women's Reproductive Lives: Unexpected Ecological Underpinnings," in the journal Cross-Cultural Research, uses insights based on life-history theory. This approach suggests that when the risks of mortality are high, women tend to reproduce more frequently (to increase the probability of some offspring surviving to maturity) and early (to ensure reproduction before they die). In fact, Low and her colleagues found that when women can expect to live to age sixty and above, the number of children they bear falls by half. Another study in 2013 by Low and her colleagues has bolstered their finding that expecting to live beyond age sixty dramatically lowers fertility.
Looking at data from various countries confirms that fertility rates do drop as the average life expectancy of women crosses the threshold of age sixty. Consider Iran. In 1970, average life expectancy for Iranian women was fifty-four and total fertility was 6.3 children. Today, Iranian women have an average life expectancy of seventy-five and bear 1.9 children. What about Bangladesh? In 1970, female life expectancy was forty-four, and they bore 6.6 children. Today, Bangladeshi women live an average of seventy years and average 2.2 children. For India the corresponding figures for 1970 were forty-eight years and 4.9 children, and are now sixty-seven years and 2.5 children. In Brazil, female life expectancy in 1970 was sixty-one and total fertility was 4.3 children. Today, Brazilian women average seventy-eight years and total fertility stands at 1.8 children. The threshold, however, is not perfectly predictive; there are lags. Female life expectancy in Mexico was sixty-five in 1970 at a time when its total fertility rate was 5.5 children. Today, Mexican women can expect to live to about seventy-eight, and they bear 2.2 children on average. For comparison, in 1970 American women could expect to live about seventy-five years, bore 2.1 children, and infant mortality was 20 per 1,000 births. In 2012, American female life expectancy had risen to eighty-one years, births averaged 1.86 children per woman, and infant mortality had fallen to 6 per 1,000 births. By the way, the only years in which the US general fertility rate was lower than 1.86 occurred during the 1970s, when the rate fell to 1.74 births in 1976.
UN demographers expect global average life expectancy at birth to rise to seventy-six by 2050 and eighty-two by 2100. If the evolutionary biologists are right, rising life expectancy will result in falling fertility. Unfortunately, the demographers estimate that life expectancy in the world's poorest countries-many of which are severely afflicted with HIV/AIDS-is now just fifty-eight, and they project that it will reach the current global average of about seventy by 2050 and eventually rise to seventy-eight by 2100.
With regard to countries where female life expectancy is below sixty years, life-history theory frequently fails to correlate well with actual fertility rates. Some countries with low female life expectancy also have relatively low total fertility rates. For example, the increased prevalence of HIV/AIDS dramatically lowered life expectancy in a lot of African countries. According to the most recent World Bank data (2011), female life expectancy in South Africa reached sixty-two years in 1990 and has now fallen to fifty-five today. Similarly, the average Namibian woman in 1990 could expect to live to age sixty-three; that has dropped to sixty-one today. In 1990 the average life expectancy for a Zimbabwean woman was fifty-nine; it is now fifty-six. In 1990, the total fertility rates for South Africa, Namibia, and Zimbabwe were 3.7, 5.2, and 5.2, respectively. Today, despite the fact that average female life expectancy has declined, totality fertility rates in those countries have fallen to 2.4, 3.2, and 3.6 children, respectively.
On the other hand, life-history predictions with regard to fertility rates do appear to pertain to lawless countries. According to the latest World Bank data (2011), female life expectancy in Mali, Nigeria, Democratic Republic of Congo, Burundi, Ivory Coast, and Afghanistan averages at fifty-four, fifty-two, forty-nine, fifty-three, fifty, and sixty years, respectively. Their corresponding total fertility rates are 6.9, 6.0, 6.1 6.2, 4.9, and 5.4 children per woman. Social, political, and economic chaos certainly afflicts those countries. George Mason University's Center for Systemic Peace has devised a State Fragility Index as a way to measure a country's stability, with scores ranging from 0, meaning no fragility, to a high of 23, denoting a failed state.
On the index, Mali scores 19, Nigeria 16, Congo 23, Burundi 18, Ivory Coast 16, and Afghanistan 22. In contrast, all twenty-two countries with a fragility score of 0 have below replacement fertility rates. Tragically, the political violence and economic chaos endemic in so many countries in sub-Saharan Africa, the ongoing food insecurity, the pervasive risk of disease, a high before-age-five child mortality rate, the lack of education, and their low social status provide African women many grounds to wonder just how long they may expect to live. Given these uncertainties, it is little wonder that fertility rates remain high on the continent as women hedge their reproductive bets.
Further insights into how the life prospects of women shape reproductive outcomes is provided in another 2010 article in Human Nature, "Examining the Relationship Between Life Expectancy, Reproduction, and Educational Attainment." That study, by University of Connecticut anthropologists Nicola Bulled and Richard Sosis, confirmed Low's findings. They divvied up 193 countries into five groups by their average life expectancies. In countries where women could expect to live to between forty and fifty years, they bear an average of 5.5 children, and those with life expectancies between fifty-one and sixty-one average 4.8 children. The big drop in fertility occurs at that point. Bulled and Sosis found that when women's life expectancy rises to between sixty-one and seventy-one years, total fertility drops to 2.5 children; between seventy-one and seventy-five years, it's 2.2 children; and over seventy-five years, women average 1.7 children. The United Nations' 2012 Revision notes that global average life expectancy at birth rose from forty-seven years in 1955 to seventy years in 2010. These findings suggest that it is more than just coincidence that the average global fertility rate has fallen over that time period from 5 to 2.45 children today.
Kids Are Expensive
Research by economists further illuminates the processes that yield falling fertility. Brown University economist Oded Galor and his colleagues have devised a unified growth theory that explains how and why people begin to focus on developing and deepening their human capital (chiefly by means of education), which then further accelerates the pace of technological progress. As a result, fertility and population growth fall, enabling humanity to escape from millennia of Malthusian stagnation into the modern world of sustained economic growth.
Recall that Malthus asserted that people on average would produce as many children as they could feed, if not more. In modern econ-speak, children are a normal good: that is to say, as income increases, demand for kids would also increase.
Instead, researchers observe that as incomes increase, the number of children per woman decreases. One possible explanation for this phenomenon is that the opportunity cost of raising children has risen over time. Opportunity cost is a benefit that must be given up to acquire or achieve something else; for example, a person may have to give up a Caribbean cruise in order to be able to buy a new car. In this case, a parent would be forgoing the extra income he or she would earn working and instead spend the time rearing a child. According to this analysis, the price of children measured in forgone income rises over time, lowering demand for them.
However, Galor points out that during the initial stages of the Industrial Revolution, as incomes were increasing in Western Europe, average fertility was increasing, just as Malthus predicted. (In contrast, US fertility rates fell throughout the nineteenth century, from 7 children per white woman in 1800 to 3.5 in 1900.) Galor suggests that the opportunity cost argument for fertility decline is too simple. If income had been the key determinant, one would find that fertility should fall as any country reaches a specific level of average per capita income. Instead, Galor notes that at the end of the nineteenth century, fertility rates begin to plummet simultaneously for a number of Western European countries at very different per capita income levels.
Galor argues that fertility began to fall as Western European economies developed increased demand for human capital during what he calls the second phase of the Industrial Revolution. In this analysis, initial increases to average incomes produced by technological progress resulted in parents' increasing both the quantity and quality of their children. However, toward the end of the nineteenth century, Galor asserts, "further increases in the rate of technological progress induced a reduction in fertility, generating a decline in population growth and an increase in the average level of education."
As economic growth was increasingly fueled by the development of ever more complicated technologies and management services, the premium attached to education began to increase. The result is that parents switched from having more children to investing in fewer higher quality (more educated) children.
Galor further argues that at the turn of the twentieth century, international trade encouraged fertility rates to fall further as rich countries began to specialize in the production of the sorts of goods that required a lot of human capital to make. On the other hand, Galor contends that poor countries increasingly specialized in goods that required a lot of manual labor to produce. The result was rising income for both rich and poor countries, but a fateful divergence in fertility trends.
During the twentieth century, fertility rates basically continued to fall in rich countries as they invested in more human capital, especially in higher levels of education. In addition, as demand for human capital grew in rich countries, schooling expanded to include women, who then entered the paid workforce. This further raised the opportunity costs of having children and encouraged further reductions in fertility.
On the other hand, poor countries channeled a larger share of their gains from increased international trade into producing more children. As a consequence, "the demographic transition in these nonindustrial economies has been significantly delayed," asserts Galor, "increasing further their relative abundance of unskilled labor, enhancing their comparative disadvantage in the production of skill-intensive goods, and delaying their process of development."
OECD economist Fabrice Murtin concurs with Galor that education is the key to lower fertility rates. In his 2009 study "On the Demographic Transition," Murtin assembled data from seventy-one countries from 1870 to 2000, to conclude that "education, rather than income or health-related variables, is the most robust determinant of the birth rate, potentially explaining about 50 to 80 percent of its decrease when average schooling grows from 0 to 10 years." Galor cites data showing that the percentage of British children ages six to fourteen who were in school rose from about 10 percent in 1860 to more than 80 percent by 1895.
As noted previously, demographer Wolfgang Lutz argues that it's not just more education, but specifically more schooling for girls that correlates with deep cuts in fertility rates. For instance, the fertility rate for Ethiopian women with no formal education was 6.1 children in 2005 and 2.0 for women with secondary and higher education. Providing women access to higher education is associated with longer lives for themselves and lower child mortality. Lutz calculates that world population in 2060 would be 1 billion fewer if the education of women globally could be speeded up to the rate achieved by South Korea in the 1960s and 1970s.
As Galor noted, the demographic transition was delayed in many poor countries, but in the second half of the twentieth century these countries also began to see rapid declines in their fertility rates. Bucknell University political scientist John Doces finds that increasing international trade is now propelling the demographic transition throughout much of the developing world. In fact, as global fertility declined since the 1950s, the value of world merchandise exports during the same period has soared by nearly ninety times.
In his 2011 study "Globalization and Population: International Trade and the Demographic Transition," Doces looks at recent data from a large number of countries and finds that those that are most open to international trade are the ones experiencing the fastest decline in their fertility rates. Doces argues that the primary cost of having children is the time and money it takes to raise them, which leaves parents less time to consume other goods. International trade expands the types of goods people can enjoy and lowers their costs. The cost of rearing children does not decline substantially, so they become more expensive relative to the new opportunities and goods afforded by increased international trade.
In addition, Doces cites a 2006 study analyzing the effects on globalization on women in 180 countries that shows "increasing international exchange and communication create new opportunities for income-generating work and expose countries to norms that, in recent decades, have promoted equality for women."46 As a result, trade-induced demand for human capital expands to include women, further cutting fertility rates in poor countries. This conclusion is further bolstered by a 2005 study by University of Helsinki economists Ulla Lehmijoki and Tapio Palokangas; according to this study, in the short run trade liberalization boosts birth rates, but in the long run it cuts fertility. Again, this is true largely because trade liberalization encourages the development of women's human capital (education), which makes childbearing relatively more costly.
The Invisible Hand of Population Control
In 2002, Seth Norton, an economics professor at Wheaton College in Illinois, published a remarkably interesting study, "Population Growth, Economic Freedom, and the Rule of Law," on the inverse relationship between prosperity and fertility. Norton compared the fertility rates of over a hundred countries with their index rankings for economic freedom and another index for the rule of law. "Fertility rate is highest for those countries that have little economic freedom and little respect for the rule of law," wrote Norton. "The relationship is a powerful one. Fertility rates are more than twice as high in countries with low levels of economic freedom and the rule of law compared to countries with high levels of those measures."
Norton found that the fertility rate in countries that ranked low on economic freedom averaged 4.27 children per woman, while countries with high economic freedom rankings had an average fertility rate of 1.82 children per woman. His results for the rule of law were similar: fertility rates in countries with low respect for the rule of law averaged 4.16, whereas countries with high respect for the rule of law had fertility rates averaging 1.55.
Economic freedom and the rule of law occur in politically and economically stable countries and produce prosperity, which dramatically increases average life expectancy and lowers child mortality; this in turn reduces the incentive to bear more children. As data from the Heritage Foundation's Index of Economic Freedom shows, average life expectancy for free countries is over eighty years, whereas it's just about sixty-three years in repressed countries.
Let's take a look at two intriguing lists. The first is a list of countries ranked on the 2013 Index of Economic Freedom issued by The Wall Street Journal and the Heritage Foundation. Then compare the economic freedom index rankings with a list of countries in the 2013 CIA World Factbook ranked by their total fertility rates. Of the thirty-five countries that are ranked as being economically free or mostly free, only two have fertility rates above 2.1-the United Arab Emirates at 2.36 and Jordan at 3.61. If one adds the next fifty countries that are ranked as moderately free, one finds that only five out of eighty-five countries have fertility rates above 3, all of them in sub-Saharan Africa except Jordan. It should be noted that low fertility rates can also be found in more repressive countries as well-for example, China at 1.55, Cuba at 1.46, Iran at 1.85, and Russia at 1.61.
In addition, along with increased prosperity comes more education for women, opening up more productive opportunities for them in the cash economy. This increases the opportunity costs for staying at home to rear children. Educating children to meet the productive challenges of growing economies also becomes more expensive and time consuming.
Thailand's experience over the past thirty years exemplifies this process. During that time, female literacy rose to 90 percent; 50 percent of the workforce is now female; and fertility fell from 6 children per woman in the 1960s to 1.5 today. Although Thailand is classified as only moderately free on the economic freedom index, its gross domestic product (GDP) grew in terms of purchasing power parity from just over $1,000 per capita in 1960 to over $8,500 per capita in 2012.
Back in 1968, Garrett Hardin declared, "There is no prosperous population in the world today that has, and has had for some time, a growth rate of zero." That's no longer true. Japan is now experiencing a fall in its population due largely to reduced fertility, as are Germany, Russia, Italy, Poland, and some 20 other countries and territories. And as we have seen, the global total fertility rate is rapidly decelerating. Of the 231 countries and territories listed in the 2013 CIA World Factbook, 122 are at or below replacement fertility rates.
Norton persuasively argues that Hardin's fears of a population tragedy of the commons are actually realized when the invisible hand of economic freedom is shackled. Many poor countries have weakly specified and enforced property rights. Poor property rights means that many resources are effectively left in open-access commons where the incentive is to grab what one can before another individual gets it. Norton points out that in such situations, more children mean more hands for grabbing unowned and unprotected resources such as water, fodder, timber, fish, and pastures, and for the clearing of land. Lacking the institutional incentives to invest in and preserve resources, this drive to take as much as possible as quickly as possible leads to perpetual poverty.
And what about in the past? Haven't societies collapsed due to overpopulation? To the extent it is true that some societies have suffered collapses, we now know that it was because they lacked the proper social, political, and economic institutions for channeling individual striving into a process of economic growth that ultimately promotes the accumulation of human capital and lower fertility. Very few, if any, earlier societies could be characterized as either economically free or respectful of the rule of law. Throughout history, most people lived in the institutional equivalents of open-access commons overseen by rapacious elites who encouraged high fertility rates and the plundering of natural resources. It turns out that economic freedom and the rule of law are the equivalent of enclosing the open-access breeding commons, causing parents to bear more and more of the costs of rearing children. In other words, economic freedom actually serves as an invisible hand of population control.
Hope for Africa?
The United Nations' 2012 Revision forecasts that more than half of global population growth between now and 2050 will take place in Africa, rising from 1.1 billion to 2.4 billion. The middle-variant trend for sub-Saharan Africa projects that total fertility rate will fall from 4.9 children now to 3.1 by 2050, reaching 2.1 by 2100. As noted above, a more worrying study published in an October 2014 issue of the journal Science suggested that by 2100 Africa's population would grow even faster, rising from 1.1 billion to between 3.1 and 5.7 billion, with a median projection of 4.2 billion.
But is it plausible that much of Africa and many of the other least developed countries will remain high-fertility basket cases for the next several decades while the rest of the world modernizes, with concomitant improvements in the life prospects of women? Surely it is reasonable to expect that new medicines, vastly more productive crops and farming techniques, high quality education delivered via low-cost computerized tablets, cheap decentralized energy, and 3-D printing of tools and goods will spill over from the labs and factories of rich countries. These modern tools will go a long way toward ameliorating the chaos and poverty currently afflicting the least developed nations. In addition, the continuing global abatement of violent conflict is already taking hold in Africa and in other poor countries. For example, in October 2014, U.S. Naval War College researcher David Burbach and Tulane University political scientist Christopher Fettweis pointed out that "after the year 2000, conflict in Africa declined, probably to the lowest levels ever." While they noted an uptick in battle deaths on the continent between 2010 and 2013, those casualties were still almost 90 percent lower than the average in the last decade of the twentieth century. "Changes in external support and intervention, and the spread of global norms regarding armed conflict, have been most decisive in reducing the levels of warfare in the continent," they concluded. "Consequently, there is no Africa exception to the systemic shift toward lower levels of armed conflict."
Among the regions of the world, according to UNESCO, adult and youth illiteracy are highest in sub-Saharan Africa. For example, among Africans aged fifteen through twenty-four, the male literacy rate stands at 76 percent versus the female rate of 64 percent. Obviously, the more that donors from rich countries can do to promote the education of women in the world's poorest countries, the better. In addition, Africa is rapidly urbanizing, which will also push fertility rates lower. For example, a 2000 study by researchers at Pennsylvania State University and Tulane University reported that African urbanites had nearly two fewer children than did their rural counterparts. Demographers working for the International Food Policy Research Institute found in 2012 an even greater urban-rural differential; Ethiopian women in the countryside had a total fertility rate of 6 offspring, whereas their city sisters averaged only 2.4 children.
This process of modernization will bring dramatic improvements in health and longer lives, resulting in a steep decline in fertility rates. Consider that the life expectancy of Bangladeshi women rose from forty-four in 1970 to seventy-two today. In addition, literacy among Bangladeshi women aged fifteen to twenty-four climbed steeply from 38 percent in 1991 to 80 percent today, actually surpassing the male rate of 77 percent. Consequently, the country's total fertility rate fell in just the twenty years between 1980 and 2000 from 6.6 to 2.9 children. It is now 2.2 children. If the current high fertility countries can realize the bare elements of political stability and economic freedom attained by Bangladesh, with its $750 per capita income, women will live longer and have fewer children. If this analysis is right-and most of the evidence points to that conclusion-the latest UN population projections will turn out to be too high and the musty Malthusian specter will finally fade away.
In his 2013 book The Infinite Resource: The Power of Ideas on a Finite Planet, technologist Ramez Naam asks an intriguing question: "Would your life be better off if only half as many people had lived before you?" In this thought experiment, you don't get to pick which people are never born. Perhaps there would have been no Newton, Edison, or Pasteur, no Socrates, Shakespeare, or Jefferson. "Each additional idea is a gift to the future," Naam writes. "Each additional idea producer is a source of wealth for future generations." Fewer people mean fewer new ideas about how to improve humanity's lot.
Instead of disdaining fellow human beings as a cancer or a plague, as modern neo-Malthusians do, Naam rightly argues, "If we fix our economic system and invest in the human capital of the poor, then we should welcome every new person born as [a] source of betterment for our world and all of us on it."
Copyright © 2015 by Ronald Bailey