1. Division of Gastroenterology and Hepatology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA;
2. Center for Access & Delivery Research and Evaluation (CADRE), Iowa City VA Health Care System, Iowa City, Iowa, USA;
3. Department of Community and Behavioral Health, College of Public Health, University of Iowa, Iowa City, Iowa, USA;
4. Department of Biostatistics, College of Public Health, University of Iowa, Iowa City, Iowa, USA;
5. Department of Health Management and Policy, College of Public Health, University of Iowa, Iowa City, Iowa, USA;
6. Department of Economics, University of Iowa, Iowa City, Iowa, USA;
7. National Bureau of Economic Research, Cambridge, Massachusetts, USA.