Projected world population numbers have been boosted 600 million by the demographers at the United Nations in the latest report, World Population Prospects: The 2012 Revision. Why are the projections going up? One big reason is the lack of economic freedom and the rule of law in most high fertility countries. Consequently, the new estimates of the middle variant projections of future population in 2050 increased from 9 billion in the U.N.'s 2010 Revision to 9.6 billion and from 10 billion to 10.9 billion by 2100. However, recent research on how life-history affects human fertility suggests that increasing economic freedom combined with the rapid diffusion of cheap modern technologies will likely push future population growth significantly below the new projections.
The U.N.'s middle variant projection is generally taken to be the most likely path of future population growth. The difference the 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."
The United Nations demographers have boosted their projections based on new data showing higher total fertility rate trends mostly in the world's least developed countries, especially those in sub-Saharan Africa. Total fertility rate is broadly defined as the number of children a woman is projected to bear over the course of her lifetime. Overall since 1960, the global total fertility rate has fallen from about 5 children per woman to 2.4 children today. It is not just a coincidence that the global fertility rate fell as economic freedom increased across the globe over the past several decades. Increased economic freedom and the prosperity and better health it produces gives people the confidence that the children they do choose to have will likely survive and even thrive.
The fertility replacement rate is about 2.1 children per woman. The 2012 Revision estimates that 48 percent of the world's population lives in countries with below replacement rate fertility, the largest of which are China, the United States, Brazil, Russia, Japan, and Vietnam. According to the Fraser Institute's Economic Freedom of the World 2012 report, China's index number increased from 3.74 in 1980 to 6.16 in 2010; Brazil from 3.83 to 6.42; Russia from 4.43 in 1995 to 6.35; Japan from 6.88 to 7.61, and Vietnam has just begun to be measured, but the trend is toward more economic freedom; and the United States fell from 7.92 to 7.70.
Another 43 percent live in intermediate fertility countries with total fertility rates between 5 and 2.1 children. The largest of these countries are India, Indonesia, Pakistan, Bangladesh, Mexico, and the Philippines. Indonesia's economic freedom index number rose from 5.09 to 7.04; Pakistan from 4.3 to 5.94; Bangladesh from 3.38 to 6.43; Mexico from 5.13 to 6.65; and the Philippines from 5.33 to 7.06. Nine percent live in countries where the average woman bears more than five children, of which 29 are in Africa, and two are in Asia. All with very low economic freedom index scores.
The 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 medium variant trend for Africa projects that total fertility rate will fall from 4.9 children now to 3.1 by 2050 reaching, 2.1 by 2100. Why is Africa's fertility so high and what are the prospects that might fall faster than the U.N. demographers predict?
Recent research applying insights from evolutionary biology may answer the first question and offer the possibility that Africa might experience the demographic transition to lower fertility rates sooner than the 2012 Revision assumes. 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 Studies uses insights based on life-history theory, an approach that 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 death. In fact, Low and her colleagues found that when women can expect to live to age 60 and above, the number of children they bear falls by half.
Another 2010 study, "Examining the Relationship between Life Expectancy, Reproduction, and Educational Attainment," in Human Nature by University of Connecticut anthropologists Nicola Bulled and Richard Sosis confirmed Low's finding. They divvied up 193 countries into five groups by their average life expectancies. In countries where women could expect to live to between 40 and 50 years, they bear an average of 5.5 children and those with life expectancies between 51 and 61 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 61 and 71 years, total fertility drops to 2.5 children; between 71 and 75 years, it's 2.2 children; and over 75 years, women average 1.7 children. The 2012 Revision notes that global average life expectancy at birth rose from 47 years in 1955 to 70 years in 2010. Recall that over that time the average global fertility rate fell from 5 to 2.4 children today.
The crucial point is that increasing economic liberty correlates with increasing life expectancies, and thus falling fertility rates. As data from the Heritage Foundation's Economic Freedom Index shows, average life expectancy for free countries is over 80 years, whereas it's just about 63 years in repressed countries.
Let's look at some data from various countries to see if fertility rates do drop as countries cross the age 60 threshold. Consider Iran. In 1970, average life expectancy for Iranian women was 54 years and total fertility was 6.3 children. Today, Iranian women average 75 years, and bear 1.9 children. What about Bangladesh? In 1970, female life expectancy was 44 years, and they bore 6.6 children. Today, Bangladeshi women live an average of 70 years and average 2.2 children. For India the corresponding figures for 1970 were 48 years and 4.9 children, and are now 67 years and 2.5 children. In Brazil, female life expectancy in 1970 was 61 years and total fertility was 4.3 children. Today, Brazilian women average 78 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 65 in 1970 at a time when its total fertility rate was 5.5 children. Today, Mexican women can expect to live to about 78 and they bear 2.2 children on average. By the way, in all of these countries economic freedom increased from 1980 until now.
The U.N. demographers expect global average life expectancy at birth to rise to 76 years by 2050 and 82 years 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 58 years and they project that it will reach the current global average of about 70 years by 2050 and eventually rise to 78 years by 2100.
With regard to countries where female life expectancy is below 60 years, life-history theory often fails to correlate well with their 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. Female life expectancy in South Africa reached 65 years in 1990 and has now fallen to 60 today. Similarly, the average Namibian woman in 1990 could expect to live to age 64, fell to 56 in 2000 and now up to 66 years today. In 1990 the average life expectancy for a Zimbabwean woman was 64 years, fell by 2000 to just 43 years, and is now up to 55 years. Today the total fertility rates for South Africa, Namibia, and Zimbabwe are relatively low for Africa at 2.4, 3.1, and 3.5 children.
On the other hand, life-history predictions with regard to fertility rates do appear to pertain to countries such as Mali, Nigeria, Democratic Republic of Congo, Burundi, Ivory Coast, and Afghanistan where average female life expectancy stands at 53, 54, 51, 54, 60, and 61 years, respectively. Their corresponding total fertility rates are 6.9, 6, 6, 6.1, 4.9, and 5 children. Social, political, and economic chaos afflict 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 22 countries with a fragility score of 0 have below replacement fertility rates. Evidently, the political violence and economic chaos that afflict so many countries in sub-Saharan Africa, pervasive disease risks, high before age-5 child mortality, and their social low 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.
Is it plausible that much of Africa and other least developed countries will remain basket cases for the next several decades while the rest of the world modernizes with concomitant improvements in the life prospects of women? Back in 1798, economist Robert Thomas Malthus predicted in his An Essay on the Principle of Population that growing human numbers would eventually outstrip available resources resulting in permanent misery of disease, starvation, and early death for some portion of the population.
I am generally an optimist who celebrates the human creativity that has engendered so much technological and moral progress in the past couple of centuries. So I am confident that new medicines, vastly more productive crops, 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 of rich countries and overcome the chaos and poverty that currently afflict the least developed nations. In addition, the continuing global abatement of violent conflict will take hold on in Africa and in other poor countries. And the more that donors from rich countries can promote the education of women in the world's poorest countries, so much the better.
The outcome this process of modernization will be dramatic improvements in health and longer lives resulting a steep decline in fertility rates. Note that the Bangladeshi total fertility rate fell from 6.6 to 2.9 children in just 20 years between 1980 and 2000. If the current high fertility countries can realize the barest elements of stability and economic freedom attained by Bangladesh with its $700 per capita income, women will live longer and have fewer children. If I am right, the latest U.N. population projections will turn out to be too high and Malthusian fears will recede.