1. Department of Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, UK
2. Department of Public Health, School of Health and Related Research, University of Sheffield, UK
3. Department of Information Studies, University of Sheffield, UK
4. Department of Probability and Statistics, University of Sheffield, UK
5. The Royal Hallamshire Hospital, Glossop Road, Sheffield, UK
6. Michael Carlisle Centre, Sheffield Care Trust, Sheffield, UK
7. University of Wisconsin-Madison, Madison, Wisconsin, USA
8. Brigham and Women's Hospital, Boston, Massachussetts, USA