Usefulness of factor and cluster analysis in grouping census tracts.

CENSUS TRACTS are useful demographic and statistical units of study. Within the larger circumscribed community, they are especially useful for determining subpopulation characteristics and subpopulations at risk to inadequate care, disease, and mortality. Officials participating in community health planning have expressed a strong interest in studies using census tract data. A recent report by the Study Group on the 1970 Census and Vital and Health Statistics suggests that the availability of such small area data "presents an excellent opportunity for those who are responsible for vital records systems to produce complementary data necessary for health planning, demography, and general social research" (1). Census tracts provide useful basic statistical units for comparing vital rates only when both the number of events (the numerator) and the population at risk (the denominator) for each tract are adequate. To solve the problem of a numerator, the investigator can extend his observations to 3 Dr. Lehr was a research associate and Dr. Rogers was professor of public health and medical administration, School of Public Health, University of California, Berkeley, at the time of this study. Dr. Messinger is a fellow at the Institute of Health Research, Berkeley. This study was supported in part by a Taxonomic Community Health Analysis grant HS-0012 from the Public Health Service and by General Research Support grant 5-S0J-R-05441 from the National Institutes of Health. Computer services were supplied by Franck Oechsli, School of Public Health Statistical Services, and vital statistics data were supplied by the San Francisco Department of Public Health and Dr. Victor Eisner, clinical professor of maternal and child health, at the school of public health. Tearsheet requests to Dr. Irene Lehr, 1786 Spruce St., Berkeley, Calif. 94709.