The Oldest-Old: Emergence of a New Population

Abstract

Although we know that the number of nonagenarians and centenarians is rapidly increasing in low mortality countries, monitoring this development with accuracy remains difficult. Basic information on the number of centenarians comes from censuses. They make it possible to adjust annual population counts and to provide annual estimates of the number of centenarians, from which we can estimate the Centenarian Doubling Time (CDT). The registration of deaths, year after year, provides a much more accurate indication of the increase in the number of centenarians than do series of censuses. We propose that the Centenarian Rate (CR), i.e., the ratio of the number of centenarians to the number of people belonging to the same cohort — aged 60 years 40 years before — per 10,000 persons, allows us to assess the importance of the number of centenarians in many countries today with simple empirical data.