Population dynamics are more complex than we thought. Fertility rates generally decline as development rises, and this has indeed been happening in most industrialized nations. Birthrates in Italy, Germany, and Japan, for instance, have dipped to 1.3 children or fewer per woman. But recently a team of sociologists in the United States and Italy revealed a twist in this pattern. When development—measured by income, education, and life span—improves past a certain point, they find, fertility picks up again. The study was published in August in the journal Nature.
The anticipated boost in fertility rates is not large enough to alter projections that the global population will level off by midcentury, says study coauthor Hans-Peter Kohler, a sociologist at the University of Pennsylvania. In fact, birthrates in most highly developed countries are still too low to maintain the national population. (The United States is an exception, with fertility rates near the replacement level of 2.1 births per woman.) But the new analysis may provide some relief for nations that fear they soon will not have enough middle-aged workers to support their growing elderly population.
The researchers are now investigating why a wide range of developed countries, despite their differing social structures, appear to be experiencing a similar and unexpected uptick in birthrates. “There is clearly not a one-size-fits-all set of institutions and policies that facilitate higher fertility,” Kohler says.