Why Is It Useful to Measure Incidence and Prevalence

I shall organize my response to these questions after the model set by J. N. Morris (1964) in his classic Uses of epidemiology. I shall argue that measurement contributes to rational policies (including, I should add, allocation of funds), to the planning of appropriate services for affected individuals and families, to the elucidation of cause, and to the achievement of prevention. Epidemiological studies of mental retardation have, in the more developed countries, proved their usefulness in relation to each of Morris Ts four purposes. Certainly in Australia, Britain, Canada, France, Germany, Ireland, Israel, the Netherlands, Scandinavia, and the United States their role is sufficiently well recognized to make it unnecessary to labor the point further. In the developing countries, however, for reasons that may emerge in our discussions, studies of incidence and prevalence have been attempted only very rarely. This is the gap this workshop is seeking to lessen. The most important question for us, then, is: Is there the same need for epidemiological studies of mental retardation in the de-