Shift and Compression of Mortality at Old Age: A Conservative Scenario

Formal relations are used to demonstrate inability of the relational Brass mortality model to keep up with declining mortality at old age. In order to adjust the model, a descriptive study is undertaken of mortality shifts at old age. To this end, ages X(M) at given levels of the mortality rate are studied. When arranged as functions of the life expectancy at birth, those ages show increasing steepness of the trend. This pattern is explained by approaching, as mortality declines, to upper limits of period mortality compression. In order to take this changing pattern into account, we obtain empirical lower-bound limits to X(M) and fit a quadratic regression lines to the lower bounds. Our models of lower-bound limits may be useful both in examining tendencies in period mortality shift and compression and as a starting point in adjusting the mortality projection models at older age. They may also be useful in the continuing discussion of prospects for further mortality decline