Apostolos Tsiachristas1, Ewout van Ginneken2, Mieke Rijken3. 1. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford, United Kingdom. 2. Berlin University of Technology, Faculty of Economics and Management, Department of Health Care Management, Straße des 17. Juni 135, 10623 Berlin, Germany; European Observatory on Health Systems and Policies, Berlin Area, Germany. 3. NIVEL (Netherlands institute for health services research), P.O. Box 1568, 3500 BN Utrecht, The Netherlands. Electronic address: m.rijken@nivel.nl.