1. Department of Preventive Medicine and Public Health Ajou University School of Medicine Suwon Korea
2. Institute of Health Services Research Yonsei University College of Medicine Seoul Korea
3. Department of Preventive Medicine Yonsei University College of Medicine Seoul Korea
4. Department of Hospital Administration, Graduate School of Public Health Yonsei University Seoul Korea
5. Department of Biostatistics, Graduate School of Public Health Yonsei University Seoul Korea