Good health is harder to define than bad health (which can be equated with the presence of disease), because it must convey a concept more positive than mere absence of disease, and there is a variable area between health and disease. Health is clearly a complex, multidimensional concept. Health is, ultimately, poorly defined and difficult to measure, despite impressive efforts by epidemiologists, vital statisticians, social scientists and political economists. Each individual’s health is shaped by many factors, including medical care, social circumstances, and behavioural choices.