The Characteristics Approach to the Study of Population Ageing

Warren C. Sanderson and Sergei Scherbov
Conventional studies of population ageing include changes in age structures but not changes in the relevant age-specific characteristics of people and, as a result, produce misleading results. Changes in the characteristics of people, such as in their remaining life expectancies, survival rates, disability rates, and cognitive abilities, for example, are all pertinent to a full understanding of population ageing. In this paper we formally develop a systematic approach to the study of population ageing that incorporates changes in the age-specific characteristics of people. We do this by generalizing the concept of age and linking these characteristic-based age indicators to new measures of population ageing. One of these indicators divides the life course into two stages, where the ratio of the durations of the two is kept constant. For example, one of these stages could be considered to be “old age”. This indicator is useful in discussions of the demographic indexation of pension ages. When changing age-specific characteristics are taken into account, we obtain a more comprehensive picture of population ageing.