How Change in Age-specific Mortality Affects Life Expectancy

At current mortality rates, life expectancy is most responsive to change in mortality rates at older ages. Mathematical formulae that describe the linkage between change in age-specific mortality rates and change in life expectancy reveal why. These formulae also shed light on how past progress against mortality has been translated into increases in life expectancy – and on the impact that future progress may have. Furthermore, the mathematics can be adapted to study the effect of mortality change in heterogeneous populations in which those who did at some age would, if saved, enjoy a different life expectancy than those who live.