Compression of mortality (rectangularisation of the survival curve)

node · earth · Global, best measured in high-income national series

The observed change in the shape of the survival curve as mortality fell: the curve went from a long concave decline, with deaths spread across every age, to something closer to a rectangle, with most of a cohort surviving into the seventies and eighties and then dying within a comparatively narrow band. Two distinct claims are often confused under the name. The demographic claim — that the variance of age at death has fallen and the modal age at death has risen — is well supported. The clinical claim, James Fries's 1980 compression-of-morbidity hypothesis, is that the onset of chronic disability would be postponed faster than death, squeezing illness into a shorter terminal period; that one remains contested, and the persistent gap between life expectancy and healthy life expectancy is the main evidence against it. Compression is also, on its own, evidence that the ceiling has not moved: a curve that squares up against a fixed right-hand edge is a different achievement from a curve that shifts right.