Rural Urban Commuting Areas (RUCA) are assigned to ZIP Codes using population and commuting information from the Census. They form a classification scheme that distinguishes urban ZIP Codes by population size and characterizes rural ZIP Codes by their population and the strength of their association with larger urban areas. Rural ZIP Codes are differentiated by three factors; the size of their largest urban community, the proportion of that population regularly commuting to larger urban areas, and the size of the urban destinations. RUCA are defined for 2004 ZIP Codes using population and commuting information from the 2000 census.
PL_RUCA4_2004 is created using a method recommended by RUCA's developers for combining the 33 categories defined by the full RUCA into a few broader categories suitable for health care analysis. The full RUCA is collapsed into PL_RUCA4_2000 using this translation:
||1.0, 1.1, 2.0, 2.1, 3.0, 4.1, 5.1, 7.1, 8.1, 10.1
||Large rural town
||4.0, 4.2, 5.0, 5.2, 6.0, 6.1
||Small rural town
||7.0, 7.2-7.4, 8.0, 8.2-8.4, 9.0-9.2
This approach produces four classes by combining categories defined by the population and primary destination of commuting flows of a ZIP Code. The advantage of this definition is that it splits urban and rural in approximately the same way as does the OMB Metro definition but at the sub county-level, and it divides rural into three relevant and useful categories.