The hospital's ownership/control category was obtained from the AHA Annual Survey of Hospitals and includes categories for government nonfederal (public), private not-for-profit (voluntary) and private investor-owned (proprietary). Hospitals in different ownership/control categories tend to have different missions and different responses to government regulations and policies.

In the Nationwide Inpatient Sample (NIS), the HCUP data element for the hospital's ownership/control category has changed over time:

• 1988-1992 NIS - the hospital's ownership/control category is stored in the ST_OWNER data element.
• 1993-1997 NIS - this same information is stored in the H_CONTRL data element.
• 1998-2007 NIS - a revised classification for hospital ownership that utilizes collapsed categories such as "private" is included under the name HOSP_CONTROL. H_CONTRL is not available.
• 2008-2011 NIS - both H_CONTRL and HOSP_CONTROL are included in the NIS. HOSP_CONTROL is used for stratification, while H_CONTRL can be used to classify hospitals for analysis.
• Beginning with the 2012 NIS - HOSP_CONTROL is no longer available. H_CONTRL is used for stratification and can be used to classify hospitals for analysis.

In the NIS prior to 2012, H_CONTRL is missing if the data source that contributed discharge data to the HCUP database prohibits the release of hospital identifiers.