One hundred years of data on populations of public residential facilities for mentally retarded people.

Data from 100 years of formal surveys of population and administrative characteristics of public residential facilities for mentally retarded people were summarized. Sources of these data were described. Results of the studies in the areas of total population, average number of residents per institution, annual per capita cost of care, resident movement (first admissions, readmissions, discharges, and deaths), and resident-to-staff ratios were presented to show trends over the 100-year period.