Carnegie Mellon University

Highway traffic

May 22, 2020

COVID-19 Stay-at-Home Policies Reduced Emissions, Energy Use, and Likely Premature Deaths

Mara Falk
  • Director of Communications and Media Relations
  • 412-268-3486

The COVID-19 pandemic has resulted in stay-at-home policies and other social distancing efforts in the United States in the spring of 2020. A new study examined the effect of these actions on emissions and health outcomes.

The study found that nationwide, personal vehicle travel fell about 40% and electricity use dropped about 6% in March and April. This, in turn, likely reduced expected premature deaths from emissions of air pollution by approximately 25%. 

The study was conducted by researchers at Carnegie Mellon University (CMU), the University of Chicago, the University of North Carolina, Greensboro, Dartmouth College, and the University of North Carolina at Chapel Hill. It was published as a working paper with the National Bureau of Economic Research (NBER).

“Our work provides insights into the benefits and costs of policies related to social distancing, which has resulted in unprecedented changes in society and in economic activity,” explains Nicholas Muller, Associate Professor of Economics, Engineering, and Public Policy at CMU’s Tepper School of Business, who coauthored the study. “We concluded that the national environmental benefit of social distancing is $5.5 billion per month, with about 60% of this from reduced deaths.”

Researchers used cell phone data (which are reported daily for every county in the United States) to measure changes in mobility and by extension, in miles traveled, from February to April 2020. They studied hourly data on electricity use by region to estimate the changes in electricity consumption and corresponding emissions over the same period, focusing on emissions that contribute to the formation of fine particulate matter. Then they connected emissions from travel and electricity use to changes in ambient fine particulate matter and looked at the associated reductions in expected adverse health effects from exposure to pollution.

Given the declines in travel and electricity use, the study estimated the expected improvements in air quality by county, as well as expected declines in mortality. For a month of social distancing, the expected premature deaths due to air pollution from personal vehicle travel and electricity use are estimated to have declined by approximately 360 deaths per month, or about 25% of the baseline of 1,500 deaths. The study also estimated that social distancing likely resulted in about 46 million metric tons less of carbon dioxide emissions per month, or roughly a 19% decline.

By assuming a value of statistical life, a common measure of the value of reductions in the risk of mortality, of $9 million and a social cost of carbon of $50 per ton, the study estimated the environmental benefit of stay-at-home and social distancing measures in the United States at $5.5 billion per month. The benefits are primarily from larger metropolitan areas such as New York City and Los Angeles.

“By analyzing the circumstances that have resulted because of the Covid-19 pandemic and quantifying the changes in emissions from two major sectors of the economy, our work demonstrated the degree to which stay-at-home measures reduced reliance on fossil-fuel-based transportation and power generation to benefit public health,” says Steve Cicala, Assistant Professor at the University of Chicago’s Harris School of Public Policy, who coauthored the study. “Our findings are relevant not just for the current time, but also in the context of a post-COVID-19 economy in which remote work and retail delivery may be more common.”

The authors acknowledge the study’s limitations, which include not modeling potential interactions between reduced exposure to fine particulate matter and the mortality risks associated with COVID-19. Therefore, they may have underestimated actual reductions in the risk of mortality. In addition, they were unable to attribute the changes in travel and electricity use to any specific policy, but instead connected the changes to behavioral changes during the time studied.

Finally, both the study’s estimation of counterfactual emissions and the estimates of counterfactual mobility that were provided by a company that analyzed mobility data were uncertain. The authors interpreted changes in cell phone mobility data as translating directly into changes in vehicle miles traveled from light-duty vehicles and did not model intermodal substitution from public transit to personal vehicle use.

The study was partially funded by the Political Economics Initiative at the Becker Friedman Institute at the University of Chicago.


Summarized from an NBER working paper, Expected Health Effects of Reduced Air Pollution from Covid-19 Social Distancing by Cicala, S (University of Chicago), Holland, SP (University of North Carolina, Greensboro), Mansur, ET (Dartmouth College), Muller, NZ (Carnegie Mellon University), and Yates, AJ (University of North Carolina at Chapel Hill). Copyright 2020 by the Authors. All rights reserved.