Mortality Change and Lifespan Inequality

Duncan Gillespie, Stanford University
Shripad Tuljapurkar, Stanford University

In the past six decades, lifespan inequality has varied greatly within and between countries even while life expectancy has continued to increase. How and why does mortality change generate this diversity? We derive a precise link between changes in age-specific mortality and lifespan inequality, measured as the variance of age at death. Key to this relationship is a young–old threshold, below and above which mortality decline respectively decreases and increases lifespan inequality. First, we show that the threshold’s location modifies the correlation between changes in life expectancy and lifespan inequality, illustrating this over two centuries in Sweden. Second, we analyze post Second World War trajectories of lifespan inequality in a set of developed countries. Mortality change varied most at young working ages, particularly in males. We conclude that if the underlying social disparities persist at young ages, but progress against old-age mortality continues, lifespan inequality increases will become more common.