Long Range Trends in Adult Mortality: Models and Projection Methods

John Bongaarts, Population Council

This study has two objectives: (1) to test a new model for the pattern of change in age-specific adult mortality rates, and (2) to develop a new methodology for projecting future trends in adult mortality. The first part of the paper presents a test of the goodness-of-fit of the logistic model for the force of mortality using data from the Human Mortality Data Bank for females and males aged 25-109 in 14 populations. The results from this exercise suggest a new version of the logistic model which is called the shifting logistic model, because the senescent mortality function is assumed to shift to higher ages over time. This approach contrasts with the conventional view that mortality declines as adult life expectancy rises. The last part of the paper proposes a new projection method based on the shifting mortality model. The proposed method is compared with the widely used Lee-Carter procedure.