Why causality in both directions complicates research

Rich people live longer than poor people in every country that researchers have studied. In the United States today, the gap in life expectancy between the richest and poorest 1% of individuals exceeds ten years. The relationship between money and health is steepest at the bottom of the income distribution, where additional resources buy the most: when people are poor, there is a great deal that money can do for their health. 

In this week’s episode, Adriana Lleras-Muney of UCLA tells Tim Phillips that the evidence on the relationship between poverty and health is less certain than policymakers tend to assume. Causality runs in both directions: poor health is one of the fastest routes into poverty, and understanding how much of the association flows in each direction is still an active debate. Giving poor people more money does not reliably translate into better health within the timescales and amounts that most experiments can test, because the details matter: how long the transfer lasts, whether it is conditional, and what receiving it signals about a person's economic future all shape what they actually do with it.

The most consistent finding from the policy evidence is that public health insurance and access to cheap, proven preventive interventions tend to deliver more reliable health gains than cash transfers — but whether either works in practice depends heavily on the implementation and the trust that governments can build with the populations they are trying to help.

The research behind this episode:

Lleras-Muney, Adriana, Hannes Schwandt, and Laura R. Wherry. 2025. "Poverty and Health." Annual Review of Economics 17.

To cite this episode:

Phillips, Tim and Adriana Lleras-Muney, 2026. "Poverty and Health." VoxDev Talk (podcast).

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About Adriana Lleras-Muney

Adriana Lleras-Muney is Professor of Economics at the University of California, Los Angeles, where her research focuses on health economics and the relationship between socioeconomic conditions and health outcomes across the life course. The paper discussed in this episode is co-authored with Hannes Schwandt (Northwestern University) and Laura R. Wherry (NYU Wagner Graduate School of Public Service).

More VoxDev Talks on this topic

The history of cash transfers: Tim Phillips speaks with Ugo Gentilini about his research tracing 2,500 years of giving people money, from Ancient Rome to the COVID pandemic, and what history reveals about the recurring debates over when and why cash transfers work.

Improving access to and use of clean water: Tim Phillips speaks with Pascaline Dupas about why access to clean water remains one of the most cost-effective public health interventions available, and the barriers that prevent its wider adoption in low-income settings.

Related reading on VoxDev

Cash transfers reduce adult and child mortality rates in low- and middle-income countries: evidence that unconditional cash transfers have measurable effects on mortality in poor settings, with implications for how we think about the relationship between income and health.

Effective health aid: Evidence from Gavi's vaccine programme: what a large-scale vaccination programme reveals about the conditions under which targeted public health interventions can make a lasting difference in low-income countries.