Despite these trends, most people conclude from their day-to-day lives that overpopulation is a serious problem. One reason is that more than half the world's population is crowded into urban areas. The high cost of raising children in mega-cities is a prime reason that global birth rates continue to fall, yet urbanization also makes the larger trend toward depopulation difficult for most to grasp. If the downward trend in birth rates doesn't moderate and stabilize as the U.N. assumes it will, the world as a whole could be losing population as soon as midcentury. And yet few people will likely see that turning point coming, so long as humans continue to pack into urban areas and increase their consumption of just about everything.
Another related megatrend is the rapid change in the size, structure, and nature of the family. In many countries, such as Germany, Japan, Russia, and South Korea, the one-child family is now becoming the norm. This trend creates a society in which not only do most people have no siblings, but also no aunts, uncles, cousins, nieces, or nephews. Many will lack children of their own as well. Today about one in five people in advanced Western countries, including the United States, remains childless. Huge portions of the world's population will thus have no biological relatives except their parents.
And even where children continue to be born, they are being raised under radically different circumstances, as country after country has seen divorce and out-of-wedlock births surge and the percentage of children living with both of their married parents drop sharply. So not only is the quantity of children in the world poised to shrink rapidly, but on current trends, a near majority of them will be raised in ways that are today strongly associated with negative life outcomes.
Are there signs of any of these trends reversing before 2025? Only a few. The percentage of the world's population raised in religious households is bound to rise, if only because adherents to fundamentalism, whether Christians, Jews, or Muslims, tend to have substantially more children than their secular counterparts. And there are certainly many ways -- from increased automation and delayed retirement to health-care reform to the provision of baby bonuses -- for societies to at least partially adjust to the tidal shift in global demographics.
But don't count on it. To make such sweeping changes would require a widespread understanding of the century's great paradox: The planet may be bursting, but most of this new population is made up of people who have already been born. So get ready for a planet that's a whole lot more crowded -- with old people.