County geographies in most of the United States are relatively small and homogenous, so county level data is widely used to analyze information. Oregon’s 36 counties, however, vary greatly in size, geography, and population. As a result, sub-county geographies needed to be developed to more accurately represent community use of health care services. Among the established small geographic boundaries, only postal ZIP Code areas follow transportation and market patterns. ZIP Codes are also linked to a large amount of demographic, socioeconomic and health status information.
In 1985, ORH, with the help of other state and local agencies, chose ZIP Codes to be the building blocks of sub-county service areas and grouped all of Oregon’s 470+ ZIP Codes into Oregon "Primary Care Service Areas" using the following criteria:
- Health resources are generally located within 30 to 40 minutes travel time;
- Defined areas are not smaller than a single ZIP Code and ZIP Codes used are geographically contiguous and/or follow main roads;
- Defined areas contain a population of at least 800 to 1,000 or more people;
- Defined areas constitute a "rational" medical trade or market area considering topography, social and political boundaries, and travel patterns;
- Additional considerations for service areas are boundaries that:
- Are congruent with existing special taxing districts (e.g., health or hospital districts);
- Include a population which has a local perception that it constitutes a "community of need" for primary health care services, or demonstrates demographic or socioeconomic homogeneity. The population should be large enough (800-1000 or more) to be financially capable of supporting at least a single midlevel health care provider.
The criteria remain the same, but the areas are updated when necessary according to changes in population and health utilization.
Download a list of Oregon Service Areas and their ORH Urban/Rural/Frontier Designation.
Download a list of Primary Care Service Areas by race and ethnic percentage.