Working Papers
When Uber Comes to Town: Spatial Frictions and Health Care Access (Job Market Paper) [Link]
American Society of Health Economists Program Chair Award 2025
Abstract: Health care is inherently local, and geographic distance and transportation constraints create spatial frictions that limit access to care. This paper examines how spatial frictions, which endogenously arise from the geographic sorting of both patients and providers, shape health care access and patient welfare. I first exploit Uber’s staggered market entry in the U.S. as an exogenous shock to patient's travel cost in a difference-in-differences design. Using the universe of administrative claims data on Medicaid-enrolled children, I document two mechanisms through which travel costs shape health care access: how much care is consumed (market expansion effect) and which provider is chosen (substitution effect). Lower travel costs increase patients’ use of primary care visits by 4.6%, which in turn improves key health inputs, such as vaccine adherence. It also changes where care is obtained and who provides it: patients travel 5.7% farther in driving time to new providers, increase visits to doctors in areas with poor public transit, and shift toward pediatric specialists over general practitioners. To quantify the welfare impact of spatial frictions, I next estimate a structural model of primary care provider choice with latent choice constraints that account for providers' heterogeneous willingness to accept Medicaid patients. I simulate counterfactual policies that reduce spatial frictions through two channels: 1) transportation subsidies that lower the cost per minute of travel and 2) increased provider payment that expands the network of willing providers, thereby reducing the distance patients must travel. The welfare gains from these policies are heterogeneous across neighborhoods: patients in low-income areas benefit from a combination of transportation subsidies and payment increases, whereas increasing provider payment alone is more effective in middle-income areas. These results suggest a place-based policy design to expand Medicaid access.
Managing Drug Use Through Administrative Burden: Evidence from Medicaid (with Abby Alpert) [Link]
Abstract: Means-tested programs that allocate benefits to low-income individuals typically rely on administrative hurdles, rather than prices, to ration access. We study the impact of prior authorization, one of the most widely used non-price mechanisms for rationing prescription drug use in Medicaid. We introduce a Regression-Discontinuity (RD) design leveraging age-based discontinuities in prior authorization restrictions to isolate its impact from other features of insurance design. Children below (or above) a certain age must obtain prior authorization for the same drugs that children on the other side of the age cutoff can fill without prior authorization. These age cutoffs vary across plans within a state, providing a unique source of identification. We find significant reductions in prescription drug use and spending for ADHD drugs. Using novel plan-level data on prior authorization approval criteria, which allows us to identify patients eligible for treatment, we show that these effects are primarily driven by the administrative hassles of the prior authorization process rather than by improved targeting of treatment.
Taxing Prescription Drugs: Evidence from New York Opioid Tax (with Jackson Reimer) [Preliminary draft available upon request]
Abstract: Over-consumption of compulsive goods is often addressed by policymakers through corrective excise taxes. While sin taxes for prescription opioids are less common, they have been proposed at the state and federal levels in an effort to curb drug overdoses. The impact of such a tax on opioid use depends on how insurers pass through the cost to patients' out-of-pocket prices. Its welfare implications are also ambiguous because any reduced utilization may reflect declines in both clinically appropriate and inappropriate use. We study New York State's prescription opioid excise tax implemented in 2019, the first of its kind in the United States. The tax varies according to a drug product's morphine milligram equivalent, such that highly potent opioids are taxed more heavily than less potent opioids. Leveraging this variation in tax exposure, we find that the policy reduced opioid utilization among Medicaid beneficiaries. This reduction occurs through substitution from higher-dose opioids to lower-dose, less tax-exposed alternatives. We also find the policy slightly reduced prime-age county employment-to-population ratios. We do not observe an impact on drug-related deaths.
Trends in Reporting and Representation in US Alzheimer’s Clinical Trials, 1997-2023. (with Zhuoer Lin, Joseph Ross, Kien Lau, Sophia Stumpf and Xi Chen) [Link] [Submitted]
Selected Work-in-Progress
Do Regulated Price Cuts Expand Access? (with Hanming Fang, Gordon Liu, Huyang Zhang, Karen Zhang)
The Short-run and Long-run Impact of Regulated Price Cuts on Competition. (with Hanming Fang, Ming Li)
Does Medicaid Managed Care Save Money? Evidence from Two Decades. (with Jacob Wallace and Anthony Lollo)
Auctions in Selection Market: Evidence from Medicaid Managed Care Procurement. (with Catherine Ishitani, Pietro Telbaldi and Jose Ignacio Cuesta)
Publications
Occupational Differences in the Effects of Retirement on Hospitalizations for Mental Illness: Evidence from Administrative Data (with Tianyu Wang, Xi Chen and Jody Sindelar.) Economics & Human Biology, 53, 101367, 2023. [Link] [IZA No. 16545] [Media coverage: Yale Institute for Global Health, Yale Center Beijing (in Chinese)]
Small Money, Big Change: The Distributional Impact of Differentiated Doctor Visit Fee on Primary Care Utilization (with Tianyu Wang, Ke Wen and Qiuming Gao) Social Science & Medicine, 339 (2023) 116355, 2023. [Link]
Does Extreme Temperature Exposure Take a Toll on Mental Health? –Evidence from China Health and Retirement Longitudinal Study (with Yanran Chen, Xuezheng Qin and Xi Chen), Environment and Development Economics, 28(5), 486–510, 2023. [Link] [IZA No. 16092]
Economic Implications of Chinese Diagnosis-Related Group-Based Payment Systems for Critically Ill Patients in ICUs (with Zhaolin Meng, Yanan Ma, Suhang Song, Ye Li, Dan Wang, Yafei Si, Ruochen Zhang, Hao Xue, Limei Jing and Huazhang Wu). Critical Care Medicine, 48(7):e565-e573, 2020 [Link]