Service areas for ambulatory medical care.

This article evaluates three alternative definitions of physician service areas using data from the 1978 National Health Interview Survey. The three types of areas are county aggregations based on different data sources: the Bureau of Economic Analysis Economic Areas (BEAAs), Ranally Basic Trading Areas (RBTAs), and Health Care Commuting Areas (HCCAs). The three types of areas differ substantially in size, population, urbanization, and the availability of physicians. The overall percentage of physician visits outside each of the three areas was small, ranging from 3 percent for BEAAs to 5 percent for RBTAs and HCCAs. Visits by nonmetropolitan residents were about four times as likely as those by metropolitan residents to occur outside of each area. The results suggest that HCCAs are the most appropriate primary care physician service areas because they are the smallest in size and population and have the greatest variability in physician supply, yet they exhibit an amount of outside-area travel for care similar to that of the two larger types of areas.