A New Perspective on Population Ageing.

Abstract

In Sanderson and Scherbov (2005) we introduced a new forwardlooking definition of age called “prospective age” and argued that its use, along with the traditional backward-looking concept of age, provides a more informative basis upon which to discuss population ageing. Age is a measure of how many years a person has already lived. Everyone of the same age has lived the same number of years. In contrast, prospective age is concerned about the future. Everyone with the same prospective age has the same expected remaining years of life. In this paper, we first explore the concept of prospective age in detail and show, using an analytic formulation, historical data, and forecasts, that prospective age is, in most cases, insensitive to whether it is measured using period or cohort life tables. We, then, use the two age concepts in concert and demonstrate how this enriches our understanding of population ageing in developed countries since 1960.