2 Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Health Care Policy, Harvard Medical School, Department of Medicine, Massachusetts General Hospital, Both in Boston, MA, USA.
3 Department of Health Care Policy, Harvard Medical School, Department of Medicine, Massachusetts General Hospital, Both in Boston, MA, USA; National Bureau of Economic Research, Cambridge, MA, USA. Electronic address: jena@hcp.med.harvard.edu.