Dr. Hay has authored or coauthored over 80 peer-reviewed scientific articles in journals including Am J Public Heath, Health Policy, J Business and Economic Statistics, JAMA, J Human Resources, J Health Politics, Policy and Law, J Health Economics, Medical Care, Am J Cardiology, J of AIDS, Am J Hospital Pharmacy, J Royal Statistical Assoc.

Dr. Hay has served as a consultant to the U.S. Health Care Financing Administration, the U.S. Agency for Health Care and Policy Research, the U.S. Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, the U.S. Environmental Protection Agency, the Government of Hungary, the Hong Kong Centre for Economic Research, the Hong Kong Medical Executives Association, the World Bank, the California AIDS Commission, the California Medi-Cal Drug Advisory Board, the County of San Diego Medically Indigent Adult program, and the County of Sacramento Homeless Program. Dr. Hay has also written numerous health-related op-eds published in papers such as the Wall Street Journal, the San Francisco Chronicle, the San Diego Union, the Sacramento Bee and Newsday.

Dr. Hay has served as a Member of the Expert Advisory Panel on Drug Utilization Review, United States Pharmacopeial Convention; an Executive Committee member for the federally-sponsored Southern California Evidence-Based Medicine Practice Center; and a member of the JAMA Web Site HIV/AIDS Editorial Review Panel. Dr. Hay is a founding member of the Board of Directors of the International Society for Pharmacoeconomics and Outcomes Research. He is founding Editor-in-Chief of Value in Health. Currently, he is an Associate Professor of Clinical Pharmacy and Pharmaceutical Economics & Policy at the USC School of Pharmacy.