1. Division of General Internal Medicine, Perelman School of Medicine, and Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia.
2. Division of General Internal Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia.
3. Humana, Inc., Louisville, KY.
4. Division of Hematology and Oncology, Perelman School of Medicine, and Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia.