Erin Trish Faculty Headshot
Faculty Directory

Erin TrishPhD

Erin TrishPhD

Co-Director, Schaeffer Center; Associate Professor of Pharmaceutical and Health Economics

Department of Pharmaceutical and Health Economics

Erin Trish is co-director of the USC Schaeffer Center and an associate professor of pharmaceutical and health economics at USC Mann. In addition, she is a nonresident fellow in economic studies at the Brookings Institution and a scholar with the USC-Brookings Schaeffer Initiative for Health Policy.

Her research focuses on the intersection of public policy and healthcare markets, with recent projects focused on surprise medical bills, prescription drug spending, healthcare market concentration and healthcare reform. Her research has been funded by grants from the Robert Wood Johnson Foundation and the Laura and John Arnold Foundation and published in leading health policy, health economics and medical journals. She has testified in the California State Assembly and presented her research at numerous federal agencies, including the Congressional Budget Office, Federal Trade Commission, Office of the Assistant Secretary for Planning and Evaluation, and the Center for Consumer Information and Insurance Oversight. In 2018, she received the Seema Sonnad Emerging Leader in Managed Care Research Award.

Trish completed a postdoctoral fellowship at the USC Schaeffer Center and the Fielding School of Public Health at the University of California, Los Angeles. She received her PhD in health policy and economics from the Johns Hopkins Bloomberg School of Public Health and her BS in biomedical engineering from Johns Hopkins University.

    Areas of Expertise

    • Health Care Policy
    • Education

      Johns Hopkins Bloomberg School of Public Health


      Johns Hopkins University


    • Links
    • Research Focus


      Dr. Trish's research focuses on the impact of public policy on health care markets. Her recent work has evaluated the impact of insurer and hospital market concentration on health insurance premiums, the effects of rating regulations in the small group health insurance market, provider payment in Medicare Advantage, specialty drug spending, and risk adjustment.

    • Selected Articles

      Do health insurance and hospital market concentration influence hospital patients’ experience of care?

      Health Services Research
      Caroline Hanson PhD, Bradley Herring PhD, Erin Trish PhD

      2019 To examine the effects of insurance and hospital market concentration on hospital patients’ experience of care, as hospitals may compete on quality for favorable insurance contracts.

      Read More

      Geographic variation in the delivery of high-value inpatient care

      PloS One
      John Romley, Erin Trish, Dana Goldman, Melinda Beeuwkes Buntin, Yulei He, Paul Ginsburg

      2019 To measure value in the delivery of inpatient care and to quantify its variation across U.S. regions.

      Read More

      Growing Number Of Unsubsidized Part D Beneficiaries With Catastrophic Spending Suggests Need For An Out-Of-Pocket Cap

      Health Affairs
      Erin Trish, Jianhui Xu, and Geoffrey Joyce

      2018 Medicare Part D has no cap on beneficiaries’ out-of-pocket spending for outpatient prescription drugs, and, unlike Medicare Parts A and B, beneficiaries are prohibited from purchasing supplemental insurance that could provide such a cap. Historically, most beneficiaries whose annual Part D spending reached the catastrophic level were protected from unlimited personal liability by the Low-Income Subsidy (LIS). However, we found that the proportion of beneficiaries whose spending reached that level but did not qualify for the subsidy—and therefore remained liable for coinsurance—increased rapidly, from 18 percent in 2007 to 28 percent in 2015. Moreover, average total per person per year spending grew much more rapidly for those who did not qualify for the LIS than for those who did, primarily because of differences in price and utilization trends for the drugs that represented disproportionately large shares of their spending. We estimated that a cap for all Part D enrollees in 2015 would have raised monthly premiums by only $0.40–$1.31 per member.

      Read More

      Physician Reimbursement in Medicare Advantage Compared With Traditional Medicare and Commercial Health Insurance

      JAMA Internal Medicine
      Erin Trish, PhD; Paul Ginsburg, PhD; Laura Gascue, MS; et al

      2017 Question: How does physician reimbursement in Medicare Advantage compare with traditional Medicare’s rates and commercial health insurance rates?

      Read More

      Does Limiting Allowable Rating Variation in the Small Group Health Insurance Market Affect Employer Self-Insurance?

      Journal of Risk and Insurance
      Erin Trish Bradley Herring

      2016 The Affordable Care Act (ACA) imposes adjusted community rating in the small group market, which employers can avoid by self‐insuring, raising concerns about adverse selection. We evaluate the impact of limiting allowable rating variation on employer self‐insurance across industries with varied health risk, using cross‐state variation in pre‐ACA rating regulations, the nationally representative 2008–2013 KFF/HRET Employer Health Benefits Survey, and a triple‐difference regression approach. We find that lower risk employers subject to laws limiting allowable premium rating variation have a predicted probability of self‐insurance that is about 18 percentage points higher than otherwise‐similar higher risk employers, suggesting that these selection concerns are warranted.

      Read More

    • Affiliations
      • Associate Director of Health Policy, Schaeffer Center for Health Policy & Economics

    • Accomplishments

      Seema Sonnad Emerging Leader in Managed Care Research Award


    • Selected Media Appearances

      Examining surprise billing: Protecting patients from financial pain

      Brookings Institute | 04/03/2019

      A group of scholars affiliated with the USC-Brookings Schaeffer Initiative for Health Policy – Loren Adler, Matthew Fiedler, Paul B. Ginsburg, Mark Hall, Erin Trish, Erin L. Duffy, and me – recently published an analysis of out-of-network billing and associated policy solutions. My testimony today is based on that reasearch, which reflects the work of this diverse and thoughtful group of coauthors. Further, this testimony reflects my personal views and should not be attributed to the staff, officers, or trustees of the Brookings Institution...

      Read More

      State approaches to mitigating surprise out-of-network billing

      Brookings Institute | 02/19/2019

      In “State Approaches to Mitigating Surprise Out-of-Network Billing” (PDF), Loren Adler, Matthew Fiedler, Paul Ginsburg, Mark Hall, Erin Trish, Christen Linke Young, and Erin Duffy dissect why surprise out-of-network billing happens and detail a suite of potential policy responses and what impacts each would have. The paper concludes with policy recommendations to eliminate surprise out-of-network billing in a manner that reduces currently inflated health care costs...

      Read More

      Dialysis giant DaVita stands to lose up to $400 million in California midterms

      CNBC | 11/06/2018

      Supporters of the proposal say one way the reimbursements could help patients is in the form of lower premiums, Erin Trish, a research professor at the USC Price School of Public Policy, told CNBC. “Ultimately, the heart of this proposition is kind of rooted in a belief that the private payments are too high,” said Trish, whose research focuses on U.S. health insurance markets. “It’s not fair that the rates are so much higher than Medicare.”...

      Read More