HOSP_URCAT4 indicates the urban-rural designation of the hospital and is based on the county of the hospital. The four-level categorization is a simplified adaptation of the Urban Influence Codes (UIC) developed at the U.S. Department of Agriculture's Economic Research Service. The 12 categories of the UIC are combined into four broader categories that differentiate between large and small metropolitan, micropolitan, and a non-urban residual. Starting in the 2014 data, the categorization is based on the 2013 version of the UIC. Prior to 2014, the categorization is based on the 2003 version of the UIC.