1. Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee
2. Vanderbilt Center for Child Health Policy, Vanderbilt University Medical Center, Nashville, Tennessee
3. Department of Biostatistics, Vanderbilt University Medical Center, Nashville, Tennessee
4. Department of Health Policy, Vanderbilt University Medical Center, Nashville, Tennessee
5. Now with Department of Health Policy and Management, Rollins School of Public Health, Atlanta, Georgia