Research

Medical School Environments and Physician Treatment Styles

Shirley Cai and Ian McCarthy

This paper studies the impact of medical school on treatment decisions where cardiologists have considerable discretion: the usage of cardiac catheterization in partial-blockage heart attack cases. Using a mover design, we find that a 10 percentage-point increase in cath lab exposure during training increases later catheterization usage by 0.58 percentage points. This effect is not mediated by medical school rank and, together with peer effects, compounds into a 1.5 long-run multiplier on per-cardiologist cath rates.

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Nursing Home Staffing and Quality: Evidence from Japan

Karen Eggleston, Toshiaki Iizuka, Yong Suk Lee, Shirley Cai, Rosina Lin, and Carter Nakamoto

Published in Aging and Health Research, 2026

Analyzing survey data from more than 1000 Japanese nursing homes, we find that an increase in more full-time equivalent direct-care staff per resident is associated with fewer pressure ulcers.

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Formation of Physician Referral Networks: Drivers and Potential Consequences

Ian McCarthy, Shirley Cai, Pablo Estrada, and Jillian Wilkins

Under review

Focusing on PCPs who enter or relocate to a new market, we study the determinants of initial PCP–specialist networks using the universe of 2010–2018 Medicare fee-for-service claims across three distinct specialty areas: orthopedic surgery, cardiology, and dermatology. A network-formation model with two-sided fixed effects shows that sharing a common practice is the dominant factor in forming initial referral links across all three specialties, followed by geographic proximity and relatively minor effects from homophily across various demographic characteristics.

Nurse Scope of Practice Expansions and Physician Location

Shirley Cai

This study seeks to understand whether existing primary care provider supply responds to expansion of nurse scope of practice (SOP), which allows advanced practice registered nurses (APRNs) to practice independently. Leveraging staggered state adoption of such policies, I find that neither aggregate primary care physician (PCP) location nor newly practicing PCP flows respond. Results show little evidence that SOP expansion induces physicians to leave markets due to increased competition; instead, it appears to allow APRNs to provide primary care without crowding out incumbent PCPs.