Because of the phenomenon of hyper-aging in the developing world, another great variable is already changing as well: migration. In Mexico, for example, the population of children age 4 and under was 434,000 less in 2010 than it was in 1996. The result? The demographic momentum that fueled huge flows of Mexican migration to the United States has waned, and will wane much more in the future. Already, the net flow of illegal Mexican immigration northward has slowed to a trickle. With fewer children to support and not yet burdened by a huge surge of elders, the Mexican economy is doing much better than in the past, giving people less reason to leave. By 2025, young people on both sides of the border may struggle to understand why their parents’ generation built this huge fence…

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.