The inequitable geographic distribution of health care resources has long been recognized as a problem in the United States. Traditional measures, such as a simple ratio of supply to demand in an area or distance to the closest provider, are easy measures for spatial accessibility. However the former one does not consider interactions between patients and providers across administrative borders and the latter does not account for the demand side, that is, the competition for the supply. With advancements in GIS, however, better measures of geographic accessibility, variants of a gravity model, have been applied. Among them are (1) a two-step floating catchment area (2SFCA) method and (2) a kernel density (KD) method. This microscopic study compared these two GIS-based measures of accessibility in our case study of dialysis service centers in Chicago. Our comparison study found a significant mismatch of the accessibility ratios between the two methods. Overall, the 2SFCA method produced better accessibility ratios. There is room for further improvement of the 2SFCA method-varying the radius of service area according to the type of provider or the type of neighborhood and determining the appropriate weight equation form-still warrant further study.

Geographic information systems (GIS) are increasingly being used in public health and medicine. Advances in computer technology, the encouragement of its use by the federal government, and the wide availability of academic and commercial courses on GIS are responsible for its growth. Some view GIS as only a tool for spatial research and policy analysis, while others believe it is part of a larger emerging new science including geography, cartography, geodesy, and remote sensing. The specific advantages and problems of GIS are discussed. The greatest potential of GIS is its ability to clearly show the results of complex analyses through maps. Problems in using GIS include its costs, the need to adequately train staff, the use of appropriate spatial units, and the risk it poses to violating patient confidentiality. Lastly, the fourteen articles in this special issue devoted to GIS are introduced and briefly discussed.

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Apparent differences in the health status of blacks and whites vary according to methods of measurement, errors in the measurement process and interpretation of the measures, and types of measures used. This article uses the literature and secondary analysis of available data to explore the impact of methods on health status comparisons by race. Methods to measure health status include records, direct observations, and self-reports. Blacks generally show the greatest health deficits based on observation and least on some types of self-reports. Major types of errors in health status estimates are random errors and biases. Random errors tend to be greater for blacks because samples used to estimate their characteristics have often been smaller than white samples. Biases include noncoverage or failure to include some types of individuals in the reporting systems at all, nonresponse or lack of complete information on some persons, and use of inaccurate information due to faulty data collection or processing. Such biases tend to be greater for black persons than for whites. Their impact often is to give the illusion that blacks may be in better health than is actually the case. The types of measures that show blacks in the poorest health status are those considered to be most objective: mortality rates and some clinical examinations and health provider records. Subjective measures of dissatisfaction with health level also show blacks to be much less healthy than whites. In contrast, self-reports of illness conditions, symptoms, and restricted-activity days show blacks, particularly children, to be relatively well off compared to whites. These self-reports may be misleading due to differential perceptions of illness and reporting biases between blacks and whites. There is no doubt that measured differences in the health status of blacks and whites often reflect substance. There are also significant methodological problems, however, in comparing health status by race, which tend to underestimate the problems experienced by the black population. This article and others in this volume stress the need to know much more about the sources and impact of these methodological problems. In the meantime, these problems need to be recognized and adjusted for, where possible, when health status measures are compared. It is particularly important to consider them when policy questions of equity and resource allocation are to be decided using indicators of health status.