Doug Saunders examines the rise of the elderly and how it may affect the US:
[T]he United States appeared to be escaping the worst of the ageing trend because it has an unusually high fertility rate (averaging almost 2.1 children per family, half a child more than Canada and Europe). Most analysts assumed that this was the result of American religion or prosperity. But an important new study by economists Moshe Hazan and Hosny Zoabi has found that the real reason for larger families is the unusually large supply of low-cost babysitters and child-care workers in the US – mainly due to immigration, much of it "illegal," from Latin America. But those Central American countries and Mexico are themselves ageing fast, which will soon choke off that cheap labour supply and drive up the cost of having extra kids – which will cause the US to become less fertile and more elderly.
(Graph from Senior Journal)