This book was made possible through the support of the Robert Wood Johnson Foundation Investigator Awards program in health-policy research. We thank the foundation, and particularly the program's leaders, David Mechanic and Lynn Rogut. Enthusiastic support and keen criticism came from Marlie Wasserman, the director, and Audra Wolfe, science editor, at Rutgers University Press. Kennie Lyman, our editor, worked long hours with the authors on style and readability. Students at the University of Pennsylvania also provided useful critiques of each chapter.