With advances in modern medicine, US life expectancy steadily improved over the second half of the 20th century. But that progress masked a growing gap in mortality between poorer and richer states that started in the 1980s.

The exact reasons for this divergence are still unknown, but a paper in the Journal of Economic Perspectives helps rule out some possibilities and provides guidance about where to look next. Authors Benjamin K. Couillard, Christopher L. Foote, Kavish Gandhi, Ellen Meara, and Jonathan Skinner say that two types of explanations stand out. On the one hand, previous research has found numerous ways that state institutions and policies have affected health outcomes. And on the other hand, there are reasons to believe that behavior and culture also contribute to mortality differences.

Disentangling these two strands may be a significant challenge for future research, according to the authors.Meara, who is Professor of Health Economics and Policy at Harvard, and Foote, who is Senior Economist at the Federal Reserve Bank of Boston, recently spoke with Tyler Smith about rising geographic disparities in US mortality.The edited highlights of that conversation are below, and the full interview can be heard using the podcast player.

[Note: The views expressed herein are solely those of the authors and do not necessarily represent the views of the Federal Reserve System or the Boston Fed.]