Modifying the Lee-Carter Method to Project Mortality Changes up to 2100

Nan Li, United Nations
Patrick Gerland, United Nations Population Division

In the last half century and in countries without mortality crises, the common pattern of mortality decline is that death rate declined faster at younger ages than at older ages. In the future and in low mortality countries, however, such a pattern is believed to change. More specifically, the decline of infant and child mortality is expected to decelerate, and the reduction of old-age mortality to accelerate. In terms of the Lee-Carter method (1992), this change would require a rotation on the age pattern of mortality-decline rates. In projections of 50 years or so, dealing with the rotation was not found necessary. When the horizon extends to a century, however, the effects of this rotation remained largely unknown. In this paper, we investigate the necessity of modifying the Lee-Carter method to deal with this rotation, and provide an acceptable solution to extend the horizon of projection to year 2100.