Alastair Leyland, PhD, is professor of Population Health Statistics and associate director of the MRC/CSO Social and Public Health Sciences Unit at the University of Glasgow in Scotland, UK. He has been working in public health for over 30 years and is currently the advisor to the Research Pillar of the European Public Health Association. His research interests are in the measurement and analysis of inequalities in health, particularly using administrative data, and in the evaluation of the effects of social policies on health.

Peter Groenewegen, PhD, is a senior researcher and former director at NIVEL, the Netherlands Institute for Health Services Research, in Utrecht. He is emeritus professor at Utrecht University in the Departments of Sociology and of Human Geography. Peter was trained as a sociologist and wrote his PhD on the spatial distribution of general practitioners in the Netherlands. His research interests are in the area of international comparisons of health systems with a focus on primary health care, medical practice variations, and environment and health.