M. G. Myriam Hunink is Professor of Clinical Epidemiology and radiology, Departments of Epidemiology and Radiology, Erasmus University Medical Center, Rotterdam, The Netherlands, and Adjunct Professor of Health Decision Sciences, Department of Health Policy and Management, Harvard School of Public Health, Harvard University, Boston, MA, USA. Milton C. Weinstein is the Henry J. Kaiser Professor of Health Policy and Management and Biostatistics at the Harvard School of Public Health, and Professor of Medicine at the Harvard Medical School, Harvard University, Boston, MA, USA.