The use of zip coded population data in social area studies of service utilization.

Social area analysis (SAA) is a well-established methodology for geographically based analysis of service delivery and other health related outcome measures. However, SAA has been limited in application by the complexities of computerized geocoding and difficulties in obtaining appropriate measures of community characteristics. In this paper we demonstrate that these problems can be overcome by employing zip code as well as the unit of analysis for SAA and obtaining commercially available measures of community characteristics. Regression analyses, using New York City zip code populations as the unit of observation were used to illustrate the role of epidemiologic risk factors in predicting rates of inpatient discharge and ambulatory care visits.