In its broadest sense: “health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (WHO 1948)-1 While this definition does not lend itself naturally to measurement, it illustrates well that the concept of health is a broad and overarching one, and that health affects many aspects of life. This definition also highlights that objective health conditions and subjective aspects of health are important for everyone. Developing better measures would help not only to better assess people’s health status, but also to gauge the performance of health systems in preventing or treating ill health, and to design more effective policies.