1. In historical study of the health of the community and of the rise and fall of diseases in the population; useful �projections� into the future may also be possible.
2. For community diagnosis of the presence, nature and distribution of health and disease among the population, and the dimensions of these in incidence, prevalence, and mortality; taking into account that society is changing and health problems are changing.
3. To study the workings of health services. This begins with the determination of needs and resources, proceeds to analysis of services in action and, finally, attempts to appraise. Such studies can be comparative between various populations.
4. To estimate, from the common experience, the individual�s chances and risks of disease.
5. To help complete the clinical picture by including all types of cases in proportion; by relating clinical disease to subclinical; by observing secular changes in the character of disease, and its picture in other countries.
6. In identifying syndromes from the distribution of clinical phenomena among sections of the population.
7. In the search for causes of health and disease, starting with the discovery of groups with high and low rates, studying these differences in relation to differences in ways of living; and, where possible, testing these notions in actual practice among populations.