One of the most interesting aspects of the population aging phenomena is the remarkable diversity of the situations that countries are facing. This is partly due to the diversity of the populations themselves – we have seen that several different patterns of aging are evolving, and that, even within a particular pattern there are multiple variations. In some societies, populations are homogeneous, and the shared sense of heritage and values enhances the possibility of reform by consensus. Others are extremely heterogeneous, weaving together immigrant populations from the far corners of the world. In these societies, consensus is often more difficult to attain. But in their diversity also lies a strength, when you consider immigration as part of the solution to the demographic challenges the developed countries face.

Variations from country to country also arise from the wide range of policy choices that were made decades ago and that cannot be easily undone this late in the game. Countries that have traditionally relied on pay-go pension systems face a much different challenge than those with more integrated public and private tiers in their retirement systems, especially where the private systems have been funded and the assets invested in broadly diversified holdings. But even countries that have established significant funding for their retirement systems will not completely escape the need to make adjustments as their populations age.