Linking Period and Cohort Life-Expectancy Linear Increases in Gompertz Proportional Hazards Models

Trifon I. Missov, Max Planck Institute for Demographic Research
Adam Lenart, Max Planck Institute for Demographic Research

We derive simple formulae linking period and cohort life expectancy, as well as their rates of change, in Gompertz proportional hazards settings. They imply that a 2.5-year gain per decade in period life expectancy, observed by Oeppen and Vaupel (2002), corresponds to a 3.3-year gain on the respective cohort basis. The validity of the two theoretically derived approximate formulae, as well as the appropriateness of model assumptions, has been tested empirically on datasets from the Human Mortality Database.