Adrien Remund , Rijksuniversiteit Groningen
What does it take to become a centenarian? An obvious accounting answer to this question is to survive from one year to the next until reaching 100 years of age. Years, however, are an arbitrary unit of time that arguably does not have much meaning in terms of the human experience of growing older. Inspired by the Strehler-Mildvan theory of ageing postulating that senescence results from a progressive loss of vitality, making it progressively more difficult to withstand environmental challenges, I define a new summary measure of mortality that rests on the ability for individuals to reach a “reasonably expectable age”. In this framework, it is by successively outliving their expected age at death, defined as EAD(x) = x + e(x), thereby receiving a new (lease of) life, that some individuals eventually manage to reach old age. The number of times that an individual needs to “beat the odds”, which can be conceived as a relative unit of time, in order to reach a given target age t (e.g. 100), is a measure of how difficult it is, in a given mortality context, to reach this age. In this paper, I first formally define this measure and show how it can be computed using classic life table instruments. I then intuitively and empirically demonstrate how it can be approximated through a log-linear relationship with the probability to survive to age t. Finally, I apply it to past and current populations to shed new light on mortality trends and differentials.
Presented in Session 15. Mortality Models