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NIS File Specifications
The NIS is a set of longitudinal hospital inpatient databases included in the HCUP family. These databases are created by AHRQ through a Federal-State-Industry partnership.
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Nationwide Inpatient Sample (NIS)

Nationwide Inpatient Sample (NIS) is the largest all-payer inpatient care database in the United States, containing data on more than seven million hospital stays from approximately 1,000 hospitals. Its large sample size is ideal for developing national and regional estimates and enables analyses of rare conditions, uncommon treatments, and special populations. The following links provide file specifications for the NIS including the dataset name, number of records, and record layout.
File Specifications for the NIS

Documents are provided in ASCII text format. The amount of time it takes to access a document depends on your machine, browser and Internet connection.
2006 NIS

Core File
  • Data Set Name: NIS_2006_CORE
  • Number of Records: 8,074,825
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2006_HOSPITAL
  • Number of Records: 1,045
  • Record layout
Severity Measures File
  • Data Set Name: NIS_2006_SEVERITY
  • Number of Records: 8,074,825
  • Record layout
DX_PR_Group File
  • Data Set Name: NIS_2006_DX_PR_GRPS
  • Number of Records: 8,074,825
  • Record layout
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2005 NIS

Core File
  • Data Set Name: NIS_2005_CORE
  • Number of Records: 7,995,048
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2005_HOSPITAL
  • Number of Records: 1,054
  • Record layout
Severity Measures File
  • Data Set Name: NIS_2005_SEVERITY
  • Number of Records: 7,995,048
  • Record layout
DX_PR_Group File
  • Data Set Name: NIS_2005_DX_PR_GRPS
  • Number of Records: 7,995,048
  • Record layout
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2004 NIS

Core File
  • Data Set Name: NIS_2004_CORE.ASC
  • Number of Records: 8,004,571
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2004_HOSPITAL.ASC
  • Number of Records: 1,004
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_2004_10PCT_SAMPLE_A.ASC
  • Number of Records: 800,457
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_2004_10PCT_SAMPLE_B.ASC
  • Number of Records: 800,457
  • Record layout
Severity Measures File
  • Data Set Name: NIS_2004_SEVERITY.ASC
  • Number of Records: 8,004,571
  • Record layout
Severity 10% Sample #1
  • Data Set Name: NIS_2004_10PCT_SEVERITY_A.ASC
  • Number of Records: 800,457
  • Record layout
Severity 10% Sample #2
  • Data Set Name: NIS_2004_10PCT_SEVERITY_B.ASC
  • Number of Records: 800,457
  • Record layout
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2003 NIS

Core File
  • Data Set Name: NIS_2003_CORE.ASC
  • Number of Records: 7,977,728
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2003_HOSPITAL.ASC
  • Number of Records: 994
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_2003_10PCT_SAMPLE_A.ASC
  • Number of Records: 797,773
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_2003_10PCT_SAMPLE_B.ASC
  • Number of Records: 797,773
  • Record layout
Severity Measures File
  • Data Set Name: NIS_2003_SEVERITY.ASC
  • Number of Records: 7,977,728
  • Record layout
Severity 10% Sample #1
  • Data Set Name: NIS_2003_10PCT_SEVERITY_A.ASC
  • Number of Records: 797,773
  • Record layout
Severity 10% Sample #2
  • Data Set Name: NIS_2003_10PCT_SEVERITY_B.ASC
  • Number of Records: 797,773
  • Record layout
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2002 NIS

Core File
  • Data Set Name: NIS_2002_CORE.ASC
  • Number of Records: 7,853,982
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2002_HOSPITAL.ASC
  • Number of Records: 995
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_2002_10PCT_SAMPLE_A.ASC
  • Number of Records: 785,398
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_2002_10PCT_SAMPLE_B.ASC
  • Number of Records: 785,398
  • Record layout
Severity Measures File
  • Data Set Name: NIS_2002_SEVERITY.ASC
  • Number of Records: 7,853,982
  • Record layout
Severity 10% Sample #1
  • Data Set Name: NIS_2002_10PCT_SEVERITY_A.ASC
  • Number of Records: 785,398
  • Record layout
Severity 10% Sample #2
  • Data Set Name: NIS_2002_10PCT_SEVERITY_B.ASC
  • Number of Records: 785,398
  • Record layout
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2001 NIS

Core File
  • Data Set Name: NIS_2001_CORE.ASC
  • Number of Records: 7,452,727
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2001_HOSPITAL.ASC
  • Number of Records: 986
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_2001_10PCT_SAMPLE_A.ASC
  • Number of Records: 745,273
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_2001_10PCT_SAMPLE_B.ASC
  • Number of Records: 745,273
  • Record layout
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2000 NIS

Core File
  • Data Set Name: NIS_2000_CORE.ASC
  • Number of Records: 7,450,992
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_2000_HOSPITAL.ASC
  • Number of Records: 994
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_2000_10PCT_SAMPLE_A.ASC
  • Number of Records: 745,099
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_2000_10PCT_SAMPLE_B.ASC
  • Number of Records: 745,099
  • Record layout
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1999 NIS - Version 2

Core File
  • Data Set Name: NIS_1999_CORE.ASC
  • Number of Records: 7,198,929
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_1999_HOSPITAL.ASC
  • Number of Records: 984
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_1999_CORE10A.ASC
  • Number of Records: 719,893
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_1999_CORE10B.ASC
  • Number of Records: 719,893
  • Record layout
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1999 NIS - Version 1

Core File
  • Data Set Name: NIS_1999_CORE.ASC
  • Number of Records: 7,198,929
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_1999_HOSPITAL.ASC
  • Number of Records: 984
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_1999_CORE10A.ASC
  • Number of Records: 719,893
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_1999_CORE10B.ASC
  • Number of Records: 719,893
  • Record layout
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1998 NIS - Version 2

Core File
  • Data Set Name: NIS_1998_CORE.ASC
  • Number of Records: 6,827,350
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_1999_HOSPITAL.ASC
  • Number of Records: 984
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_1998_CORE10A.ASC
  • Number of Records: 682,735
  • Record layout
10% Sample File #2
  • Data Set Name: NIS_1998_CORE10B.ASC
  • Number of Records: 682,735
  • Record layout
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1998 NIS - Version 1

Core File
  • Data Set Name: NIS_1998_CORE.ASC
  • Number of Records: 6,827,350
  • Record layout
Hospital Weights File
  • Data Set Name: NIS_1998_HOSPITAL.ASC
  • Number of Records: 984
  • Record layout
10% Sample File #1
  • Data Set Name: NIS_1998_CORE10A.ASC
  • Number of Records: 682,735
  • Record layout
10% Sample File #2

  • Data Set Name: NIS_1998_CORE10B.ASC
  • Number of Records: 682,735
  • Record layout
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1997 NIS

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1996 NIS

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1995 NIS

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1994 NIS

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1993 NIS

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1992 - 1988 NIS

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Additional information is available on the AHRQ Website.
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Internet Citation: HCUP NIS File Specifications. Healthcare Cost and Utilization Project (HCUP). May 2008
Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/nis/nisfilespecs.jsp.
Last modified 5/13/08