1 The Lancet, London NW1 7BY, UK (RH); University of Auckland, Auckland, New Zealand (RBe, RBo); Department of Public Health, AUT University, Auckland, New Zealand (JR); Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine, London, UK (MM); and Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden (SW).