1 Department of Health Management and Health Economics, Institute of Health and Society, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Health Policy and Management, Yale School of Public Health, New Haven, Conn; Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands; LINK Medical Research, Oslo, Norway. Electronic address: n.r.kunst@medisin.uio.no.
2 Department of Paediatrics, Oslo University Hospital, Oslo, Norway.
3 Department of Paediatrics, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.