1. Division of Gastroenterology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
2. Department of Economics, University of Southern California, Los Angeles, CA, USA
3. Division of Biostatistics, Department of Biomedical Systems Informatics, Yonsei University College of Medicine, Seoul, Republic of Korea
4. Department of Economics, Yonsei University, Seoul, Republic of Korea