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_RUCA10_2004 is one method of combining the 33 categories defined by the full RUCA into broader categories. The 10 categories are created utilizing the integer portion of PL_RUCA. This approach produces categories that focus on the population size of the origins and destinations of the primary commuting flow. The secondary commuting flows that provide additional refinements concerning the connection between areas are discounted.