Longevity and the Well-Being of Populations.

• Author: Lleras-Muney, Adriana

Life expectancy has increased tremendously in the United States, from an average of roughly 47 years in 1900 to 77 years in 2020. However, increases in longevity have not been equally distributed among all subgroups of the population. Longevity is an important component of well-being, possibly as important as income; people are willing to pay very large sums to protect and increase it. Understanding the evolution and distribution of lifespan is critical to understanding changes in population well-being. In this article I discuss how my research has contributed to our understanding of these patterns.

Disparities in Childhood Environments

Lifespan is unequally distributed across space and depends on where individuals are born and where they live. For example, among women born in 1900 who survived to age 40, those born in West Virginia lived to age 76.6, while those born in North Dakota lived 3.4 years longer. Similarly, the gap between men born in the highest and lowest life expectancy states was about four years. (1) This suggests that some disparities can be traced to childhood and particularly to the environments in which children grow. But what elements of the environment matter and, more importantly, what interventions would benefit children and increase their longevity?

Perhaps not surprisingly, family income during childhood matters. Previous work has shown that the association between family income and health is small at birth but grows over the lifetime. (2) Poor children eventually turn into poor adults, and poor adults live substantially shorter lives. (3) But can governments help children growing up in poverty? Anna Aizer, Shari Eli, Joseph Ferrie, and I show that cash transfers to poor mothers given through the Mothers' Pensions program--the precursor to Aid to Families with Dependent Children--increased the longevity of their sons (Figure 1). (4) The median transfer lasted three years and amounted to roughly 30 percent of family income. Boys in families that received transfers lived more than a year longer as a result.

Previous work also has shown that individuals graduating from college in recessions have substantially higher mortality later in life, and lower lifetime incomes, than those who graduate in stronger economic circumstances. (5) But can programs that target unemployed youth undo these harms? Aizer, Eli, Guido Imbens, Keyoung Lee, and I study the impacts of the Civilian Conservation Corps, a youth employment program in place during the Great Depression that provided employment and training to unemployed men (but not women) ages 17 to 25. (6) We find that young men who participated in the training program for a longer time had greater lifetime earnings and longevity (Figure 2).

These studies show that the environments in which children grow up and the conditions in which they enter adulthood matter, and more importantly, they show that interventions to improve their circumstances can have large consequences over the lifetime, at least for men.

In both studies, we only observe intervention-related declines in mortality at older ages: there is no visible impact before age 55 or so. Why do the effects of childhood conditions manifest only later in life, and how can we predict the long-term effect of changes in the environment? To understand this, Flavien Moreau and I posit and estimate a model that tracks the evolution of health and mortality from birth to death for a given cohort and use it to understand the effects of temporary and permanent shocks. (7) The model predicts that adverse conditions throughout life will have nonlinear effects on health and mortality. The gap in mortality rates between affected and unaffected populations is U-shaped (Figure 3, right axis). Early on, adverse circumstances increase mortality. But because of selective mortality--the least healthy die--and health...