The UN projects that over the next 40 years, more than half of the world's population growth will come from people over 60. That could drastically change the flow of 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.
The Dish 