National Geographic : 2011 Jan
• than anyone had anticipated. Since then, the population growth rate has fallen by more than 40 percent. THE FERTILITY DECLINE that is now sweeping the planet started at di erent times in di erent coun- tries. France was one of the rst. By the early 18th century, noblewomen at the French court were knowing carnal pleasures without bearing more than two children. ey o en relied on the same method Leeuwenhoek used for his studies: with- drawal, or coitus interruptus. Village parish re- cords show the trend had spread to the peasantry by the late 18th century; by the end of the 19th, fertility in France had fallen to three children per woman---without the help of modern contracep- tives. e key innovation was conceptual, not contraceptive, says Gilles Pison of the National Institute for Demographic Studies in Paris. Until the Enlightenment, "the number of children you had, it was God who decided. People couldn't fathom that it might be up to them." Other countries in the West eventually fol- lowed France's lead. By the onset of World War II, fertility had fallen close to the replacement level in parts of Europe and the U.S. en, a er the surprising blip known as the baby boom, came the bust, again catching demographers o guard. ey assumed some instinct would lead women to keep having enough children to ensure the survival of the species. Instead, in country a er developed country, the fertility rate fell below replacement level. In the late 1990s in Europe it fell to 1.4. " e evidence I'm familiar with, which is anecdotal, is that women couldn't care less about replacing the species," Joel Cohen says. The end of a baby boom can have two big economic e ects on a country. e rst is the "demographic dividend"---a blissful few dec- ades when the boomers swell the labor force and the number of young and old dependents is relatively small, and there is thus a lot of money for other things. en the second e ect kicks in: e boomers start to retire. What had been considered the enduring demographic order is revealed to be a party that has to end. e sharp- ening American debate over Social Security and last year's strikes in France over increasing the retirement age are responses to a problem that exists throughout the developed world: how to support an aging population. "In 2050 will there be enough people working to pay for pensions?" asks Frans Willekens, director of the Netherlands Interdisciplinary Demographic Institute in e Hague. " e answer is no." In industrialized countries it took generations for fertility to fall to the replacement level or be- low. As that same transition takes place in the rest of the world, what has astonished demographers is how much faster it is happening there. ough its population continues to grow, China, home to a h of the world's people, is already below replacement fertility and has been for nearly 20 years, thanks in part to the coercive one-child policy implemented in 1979; Chinese women, who were bearing an average of six children each as recently as 1965, are now having around 1.5. In Iran, with the support of the Islamic regime, fertility has fallen more than 70 percent since the early '80s. In Catholic and democratic Brazil, women have reduced their fertility rate by half over the same quarter century. "We still don't un- derstand why fertility has gone down so fast in so many societies, so many cultures and religions. It's just mind-boggling," says Hania Zlotnik, director of the UN Population Division. "At this moment, much as I want to say there's still a problem of high fertility rates, it's only about 16 percent of the world population, mostly in Africa," says Zlotnik. South of the Sahara, fer- tility is still ve children per woman; in Niger it is seven. But then, 17 of the countries in the region still have life expectancies of 50 or less; they have just begun the demographic transition. In most of the world, however, family size has shrunk dramatically. e UN projects that the world will reach replacement fertility by 2030. " e popu- lation as a whole is on a path toward nonexplo- sion---which is good news," Zlotnik says. e bad news is that 2030 is two decades away and that the largest generation of adolescents in Robert Kunzig is National Geographic's senior editor for the environment.