[1] Harvard Med Sch, Dept Populat Med, Div Hlth Policy & Insurance Res, 401 Pk St,Ste 401, Boston, MA 02215 USA
[2] Harvard Pilgrim Hlth Care Inst, 401 Pk St,Ste 401, Boston, MA 02215 USA
[3] Duke Univ, Sch Med, Dept Med, Durham, NC 27706 USA
[4] Harvard Med Sch, Dept Hlth Care Policy, Boston, MA 02215 USA
[5] Harvard TH Chan Sch Publ Hlth, Dept Hlth Policy & Management, Boston, MA USA
[6] Harvard Kennedy Sch, Cambridge, MA USA
[7] Natl Bur Econ Res, Cambridge, MA 02138 USA