Advances in science and technology coupled with large-scale changes in health practices involving improved sanitation, water purification, and a host of lifestyle changes have led to dramatic increases in longevity in developed nations around the world. On a global scale, life expectancies in developed regions are continuing to rise in the 21st century and, although most people assume that there are biological limits on life span, so far there is little evidence that we are approaching them. Because fertility declined across the same years that life expectancies increased, the distribution of age in the global population changed irrevocably. The once-universal pyramid shapes of age distributions of populations in the western world, with many young ones at the bottom narrowing to tiny peaks at the tops, are being rectangularized, reflecting the fact that most people, not just an exceptional few, are living into old age.
To the extent that the importance of ageing societies is recognized at all, anxiety is the typical response. Terms like “grey tsunami” imply that larger numbers of older citizens will become a drain on societies. Concern is warranted. The demographic changes underway are fundamentally altering virtually all aspects of life as we know it. Workforces are becoming older and more age diversified than ever in history. Families are having fewer children, yet four and five generations are alive at the same time. Education has come to predict well-being and even length of life, yet is unevenly distributed, creating heightened disparities across socioeconomic strata accentuating old age outcomes between rich and poor.
 Oeppen, J. and J. W. Vaupel: Broken limits to life expectancy. Science 296, 1029-1031 (2002).