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A fascinating study by the University of Connecticut anthropologists Nicola Bulled and Richard Sosis looks at life expectancy and fertility rates in 193 countries. In the October 2010 issue of Human Nature, they report that “when life expectancy is high, educational attainment is also high, reproductive timing is delayed, and overall reproduction reduced.”
The University of Michigan ecologist Bobbi Low and her colleagues have found that once women can expect to live past age 60, they begin to have their first child later in life and have fewer children overall. Longer life expectancy is also correlated with more education for women.
Bulled and Sosis report a similar finding: Women who live in countries where life expectancy is below 50 years bear an average of 5.5 children. When life expectancy is between 50 and 60, they bear an average of 4.8 children. The big drop occurs when they can expect to live between 60 and 70 years, in which case women have about 2.5 children on average. The decline continues if women expect to live between 70 and 75 years to 2.2 children, and falls to just 1.75 children if they can expect to live older than 75.
The United Nations World Population Prospects 2010 Revision reported that world average life expectancy for women is now 70 years. Global average life expectancy in 1960 was 52 years and the total fertility rate was about 5 children per woman. As life expectancy keeps rising, average total fertility today has fallen to a world average of 2.36 children per woman, just slightly above the 2.1 replacement rate.
People Everywhere Are Getting Smarter
About half of Americans two generations ago would have been diagnosed as mentally retarded based on today’s IQ tests.
In 1980, the New Zealand political scientist James Flynn discovered that average IQs in many countries have been drifting upward at about 3 points per decade over the past couple of generations. In fact, the average has risen by an astonishing 15 points in the last 50 years in the United States. In other words, a person with an average IQ of 100 today would score 115 on a 1950s IQ test, and a person of average IQ today would have been in approximately the top 15 percent of same-age scorers 50 years ago. If the average American kid were to take the first Stanford-Binet IQ test from 1932, she would score about 124 points today.
“This means that on an IQ test made in 1930 the average score of the entire population would give an IQ between 120 and 130 according to the original standardization,” the Hungarian technologist Kristóf Kovács explains. So “instead of 2 percent, 35–50 percent of the population would have an IQ above 130. And vice versa; if the current standard was applied to people living in 1930, average IQ would be between 70 and 80, and instead of 2 percent, 35–50 percent would be diagnosed with mental retardation.”
What accounts for this massive increase in IQ scores? Researchers have suggested a panoply of causes, including better nutrition, exposure to more mentally challenging media, and more formal schooling, but my favorite is the reduced load of infectious childhood diseases.
A fascinating study published in the June 2010 Proceedings of the Royal Society by the University of New Mexico biologist Christopher Eppig and his colleagues finds an intriguing correlation between the average IQ of a country’s citizens and the intensity with which they suffer from parasites and infectious diseases. The authors note that the brains of newborns burn up 87 percent of infants’ metabolic energy; 5-year-old brains use 44 percent; and adult brains consume 25 percent of the body’s energy. Mobilizing the immune system to fight off diseases and parasites is very metabolically expensive, diverting nutrients and energy that would otherwise be used to fuel the building and maintenance of the human brain. If this analysis is substantially correct, then promoting public health also promotes higher IQs.
The new study reports, “Infectious disease remains the most powerful predictor of average national IQ when temperature, distance from Africa, gross domestic product per capita and several measures of education are controlled for. These findings suggest that the Flynn effect may be caused in part by the decrease in the intensity of infectious diseases as nations develop.”
The converse of this research should find a correlation between higher average IQs and increasing allergy and asthma rates. Allergy and asthma rates are hypothesized to be on the rise because children’s immune systems, no longer challenged by infections, have become oversensitive, attacking the bodies they are supposed to protect. Myopia also correlates with higher IQ scores; U.S. myopia rates in people ages 12 to 54 increased from 25 percent in 1971–72 to 41.6 percent in 1999–2004. But higher IQ correlates with better health and longer lives, less propensity to commit crimes, and higher income (although not greater than average personal wealth).
Trade Creates Jobs and Makes People Richer
Benjamin Franklin once declared, “No country was ever ruined by trade.” Franklin believed that the free exchange of products across borders was good for everybody, “even seemingly the most disadvantageous.” But in the 21st century, many voters and the politicians they elect believe the opposite. Being open to trade, people fear, allows rapacious corporations to “ship jobs overseas.”
A March 2011 European Economic Review study forthrightly asks the question: Does exposure to international trade create or destroy jobs? The answer strongly backs Franklin’s observation. “A 10 percent increase in total trade openness reduces aggregate unemployment by about three quarters of one percentage point,” the authors conclude. Simply put: Trade creates jobs.