1. Department of Health Services Research and Policy, Faculty of Public Health and Policy 15-17 Tavistock Place, London, WC1H 9SH, UK
2. Institute of Health Policy and Management, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
3. Department of Health Sciences, Amsterdam Public Health Research Institute, Amsterdam, The Netherlands
4. Faculty of Health, Social Care and Education, Kingston University and St George’s, University of London, St George’s Campus, 6th Floor Hunter Wing, Cranmer Terrace, London SW17 0RE, UK