The importance of income and place in U.S. life expectancy

Over the past year or so, more and better research on the life expectancies of Americans has sparked debate over possible links to rising income inequality. In November, a study by Anne Case and Angus Deaton of Princeton University raised concerns that the life expectancy for middle-aged white Americans was on the decline. While that paper has been contested, a number of other studies and data show that increases in life expectancy are accruing disproportionately to high-income Americans. A new study backs up those results while also showing that increases in the inequality of life expectancy in the United States varies quite a bit by location.

The new study is from a number of researchers, led by Stanford University economist Raj Chetty. The paper uses administrative data from tax records from 1999 to 2014. This large dataset, 1.4 billion tax records, lets the researchers look at how these trends changed not only over time but also within specific geographic areas.

The first big result isn’t a new one: So-called longevity inequality is on the rise. Chetty and his colleagues focus on the life expectancy, conditional on reaching age 40. From 2001 to 2014, the conditional life expectancy of a man in the top 5 percent of the income distribution increased by 2.34 years, and by 2.91 years for a woman. In contrast, for a man and a woman in the bottom 5 percent, the increases were only 0.32 years and 0.04 years, respectively. In other words, a woman at age 40 in the top 5 percent has gained an additional three years over a woman at a bottom, and the increased advantage for a man was about two years.

Looking at the geographic variation in these trends, however, reveals a second big result for the researchers: Life expectancy for those at the top of the income ladder doesn’t vary much across the country, but it varies significantly for those at the bottom. Areas with higher life expectancy for those in the bottom 25 percent by income tend to be the areas with the least amount of longevity inequality. In short, location matters much more for those at the bottom than those at the top.

To be clear, there isn’t any evidence here of causality. We can’t tell from this research if income causes better health outcomes or if better health outcomes affect incomes. Nor do we know whether where one lives has a causal effect on health outcomes for low-income individuals—a finding that other research by Chetty shows is related to upward income mobility. And Deaton, commenting on the paper, also notes that among a number of other factors that researchers should weigh in the balance is the importance of educational differences.

But it’s worth noting the relationship between income and location. The authors actually found a positive relationship between economic segregation and life expectancy at the bottom of the income ladder, but that’s segregation within these areas. Perhaps an inability to access certain areas may be harmful for life expectancy. There’s been increasing attention to the high cost of living in urban areas such as New York City and San Francisco, which are also areas where the life expectancy of low-income individuals is higher.

Increasing access for low-income earners to those areas of the country where life expectancy among low-income residents is high would be an important policy goal if researchers discover a causal effect. But perhaps policymakers should instead examine what factors in the research data are associated with lower longevity inequality in some areas of the country and enact policies that encourage those factors in other areas.

Unsurprisingly, areas where people smoke less, exercise more, and are less obese have higher life expectancies. And those areas tend to be areas with more immigrants, higher home prices, and more workers with college degrees. Areas with higher public expenditures also have higher life expectancies for low-income individuals. Again, these correlations come with the caveat that they are not necessarily signs of causation. For better knowledge about how to increase life expectancy in areas that lag behind, well, we’ll have to wait for more research.