Variance in Death and Mortality Decline

Shripad Tuljapurkar, Stanford University
Ryan D. Edwards, Queens College (CUNY)

Mortality change is commonly summarized in terms of trends in life expectancy, and mortality models evaluated on their ability to match historical trends. We show here that the variance of the age at death provides important additional information. We show that historical increases in life expectancy have been accompanied by striking decreases in the variance of the age of adult death. Next, we show how the variance in age of adult death can be approximately computed for any reasonable model of mortality rates, and illustrate this with the Gompertz, the logistic, and models with multiplicative frailty. Finally, we present results on world-record trends in the variance in age of adult death, and discuss the implications of our results for understanding secular mortality change.