Who you calling old?

• Position: Aging

Everyone knows that 60 is the new 50 but, now, Warren Sanderson, professor of economics at Stony Brook (N.Y.) University, and Sergei Scherbov, a project leader at an Austrian research institute, show that, counter-intuitively, population aging is slower when life expectancy increase is faster--60 really is the new 50. Their work calls into question societal understandings of age.

"If the point for being considered 'old' is changed to reflect the fact that we live longer, we get a completely different picture of future population aging," maintains Sanderson.

Thus, the conventional view that faster increases in human life expectancy lead to faster population aging actually is wrong. In fact, a more accurate understanding of age would be to view it not from time of birth but, instead, as time left until death, because this is more closely related to the infirmities and frailties that are associated with old age.

Over time, as life expectancy increases and people become healthier, older people can do things that previously were the domain of those who were younger. Consider that people older and older are doing things such as having children, achieving extraordinary feats of physical strength...