Research

Here we compile data on 1,700 local, regional and national non-pharmaceutical interventions that were deployed in the ongoing pandemic across localities in China, South Korea, Italy, Iran, France and the United States. We then apply reduced-form econometric methods, commonly used to measure the effect of policies on economic growth, to empirically evaluate the effect that these anti-contagion policies have had on the growth rate of infections. In the absence of policy actions, we estimate that early infections of COVID-19 exhibit exponential growth rates of approximately 38% per day. We find that anti-contagion policies have significantly and substantially slowed this growth. 

Article Link / Interview Link

Though air-quality alert systems (AQAS) cover more than 1.7 billion people worldwide, there has been little welfare analysis of these systems. This paper presents a theoretical framework for deriving lower bounds on the net benefits of an AQAS and applies it to a South Korean system currently covering over 51 million people. Estimating a regression discontinuity design, we find that an alert issuance reduced youth respiratory expenditures by 30% and adult cardiovascular expenditures by 23%. The overall system reduced externalized health expenditures by 28.6 million dollars during 2016−2017, with a minimum benefit-cost ratio of 7.1:1. Including dynamic impacts of alerts increases the minimum benefits (benefit-cost ratio) to 36.7 million dollars (9.2:1). Our findings imply that the AQAS generates significant net benefits and suggests that manipulation of air quality data, which has been observed in other contexts, may negatively impact social welfare.

Working Paper Link / NBER Link

Particulate matter (PM) is the most clinically important air pollutant. Current studies assume that units of PM originating in different jurisdictions cause the same harm, despite widespread understanding that differing chemical and physical features of PM could generate distinct health effects. Here, we combine an atmospheric model, universal health records, and econometric analysis to provide the first direct evidence that the health impacts of PM depend on its originating jurisdiction. We simultaneously measure harm from seven categories of PM within a single population at the nexus of the world's most contentious transboundary air pollution dispute. Because impacts differ by origin, we compute that transboundary sources contribute only 43% of anthropogenic PM load to our study population, but generate > 70% of its associated respiratory health costs. Our results indicate that PM should be considered a mixture of pollutants of distinct origins, each with a unique measurable impact on human health.

NBER Link

Regulations that restrict the operating days of large firms are often justified as a means of protecting small competitors. We study South Korea’s mandatory shutdown policy, which requires large retail chains to close one day every other week, and quantify how consumer spending adjusts along multiple margins. Using high-frequency transaction data and exploiting within-month variation in closure schedules, we document four substitution channels: diversion to independent retailers, substitution toward other unrestricted retail formats, intertemporal shifting within restricted chains, and spatial substitution across districts with different closure calendars. Only a small share of displaced spending is redirected to independent retailers, while most adjustment occurs through intertemporal substitution within restricted chains and diversion to other unrestricted retail formats operated by large chains. We find no evidence that the policy improves the long-run survival of independent retailers. Mapping observed substitution patterns into a discrete-choice framework, we estimate that consumer welfare losses from restricted access exceed the gains accruing to small retailers by a factor of 2.6, highlighting a fundamental trade-off inherent in protective regulation.