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KID Overview

Overview of the Kids' Inpatient Database (KID)

The Kids' Inpatient Database (KID) is part of a family of databases and software tools developed for the Healthcare Cost and Utilization Project (HCUP). HCUP inpatient data are based on administrative data—discharge abstracts created by hospitals for billing. The KID is the largest publicly-available all-payer pediatric inpatient care database in the United States. Unweighted, it contains data from approximately 3 million pediatric discharges each year. Weighted, it estimates roughly 7 million hospitalizations.

Developed through a Federal-State-Industry partnership sponsored by the Agency for Healthcare Research and Quality, HCUP data inform decision making at the national, State, and community levels.

This page provides an overview of the KID. For more details, see KID Database Documentation and the Introduction to the KID, 2019 (PDF file, 978 KB; HTML).


The KID yields national estimates of hospital inpatient stays for patients younger than 21 years of age. The unique design of the KID enables national and regional studies of common and rare pediatric conditions.

The KID can be used to identify, track, and analyze national trends in healthcare utilization, cost, quality, and outcomes.

The number of States in the KID has grown from 22 in the first year (1997) to 48 plus the District of Columbia in 2019.

Key features of the most recent KID database year (2019) include:
  • A large sample size, which enables analyses of rare conditions (e.g. congenital anomalies) as well as, uncommon treatments (e.g. cardiac surgery)
  • Sampled from 4,000 U.S. community hospitals (defined as short-term, non-Federal, general and specialty hospitals, excluding hospital units of other institutions), excluding rehabilitation hospitals
  • Normal newborns (with little variance) were sampled at a rate of 10%, while complicated newborns and other pediatric discharges (age 20 or less at admission) were sampled at a rate of 80%
  • Pediatric discharges of all payers, including children covered by Medicaid, or private insurance, as well as those who are uninsured
Information on the previous releases of the KID may be found in the Introduction to the KID (PDF file, 852 KB; HTML).
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KID data are available every three years from 1997 through 2012; then every three years beginning with 2016, which allows researchers to analyze trends over time. The KID was not produced for 2015 because of the transition from ICD-9-CM to ICD-10-CM/PCS coding. The KID product is downloaded in a single zipped file for each year which contains several data-related files and accompanying documentation. For 2019, there are three discharge-level files and one hospital-level file:

Discharge-level files
  • Core File is a single file containing commonly used data elements (e.g., age, expected primary payer, discharge status, ICD-10-CM/PCS codes, total charges).
    • This file is available in all years of the KID.
    • The HCUP unique record identifier (RECNUM) provides the linkage between the discharge-level files.
  • Severity File is a single file containing additional data elements to aid in identifying the severity of the condition for a specific discharge.
    • This file is available beginning with the 2003 KID.
  • Diagnosis and Procedure Groups File is a single file containing additional information on the ICD-10-CM diagnoses and ICD-10-PCS procedures that is created by the Agency for Healthcare Research and Quality (AHRQ) software tools.
    • This file is available beginning with the 2006 KID.
    • For data year 2016, this file was not available in the KID. Data elements derived from the ICD-10-CM/PCS AHRQ software tools were not included in the KID because they were still in development and testing.
    • Beginning with data year 2019, this file is available in the KID and includes data elements derived from the Clinical Classifications Software Refined (CCSR) for ICD-10-CM diagnoses, the CCSR for ICD-10-PCS procedures, and Procedure Classes Refined for ICD-10-CM.
Hospital-level files
  • Hospital File is a single file containing information on hospital characteristics.
    • This file is available in all years of the KID.
    • Linkage between the Inpatient Core File and the Hospital File
      • Prior to the 2012 KID, the HCUP hospital identifier (HOSPID) provided the linkage between the KID Inpatient Core File and the Hospital File.
      • Beginning with the 2012 KID, the KID hospital number (HOSP_KID) provides the linkage between the KID Inpatient Core File and the Hospital File. The HOSP_KID values are reassigned each year, so they cannot be used to link hospitals across years.

Users interested in applying AHRQ software tools to the KID for data years including ICD-10-CM/PCS-coded data to produce data elements currently unavailable in the database files may do so by downloading the respective tool(s) from the Research Tools section of the HCUP User Support (HCUP-US) website. Additionally, users may wish to review the HCUP Software Tools Tutorial, which provides instructions on how to apply the AHRQ software tools to HCUP or other administrative databases.
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The KID contains clinical and resource-use information that is included in a typical discharge abstract, with safeguards to protect the privacy of individual patients, physicians, and hospitals (as required by data sources). It contains more than 100 clinical and nonclinical data elements for each hospital stay, including:
  • Primary and secondary diagnoses and procedures
  • Discharge status
  • Patient demographics (e.g., sex, age, race, median income for ZIP Code)
  • Hospital characteristics (e.g., ownership, size, teaching status, Census division)
  • Expected payment source
  • Total charges
  • Length of stay
  • Severity and prior to 2016, comorbidity measures
  • AHRQ software tools (not available for 2016)
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As a uniform, multi-State database, the KID promotes comparative studies of healthcare services and supports healthcare policy research on a variety of topics, including:
  • Utilization of health services by special populations
  • Hospital stays for rare conditions
  • Variations in medical practice
  • Healthcare cost inflation
  • Medical treatment effectiveness
  • Regional and national analyses
  • Quality of care
  • Impact of health policy changes
The KID is used in a variety of publications:

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Spanning 23 years of data, the KID can be used for longitudinal analyses; however the database underwent changes in 2000. To facilitate analysis of trends including the 1997 KID, an new set of KID discharge weights for the 1997 HCUP KID were developed. These trend weights were calculated in the same way as the weights for the 2000 and later years of the KID. (Trend analyses for 2000 and later data do not need the KID trends weights.) The report, Using the Kids' Inpatient Database (KID) to Estimate Trends, includes details regarding the KID trends weights and other recommendations for trends analysis. The KID trends report is available on the HCUP-US website at, and the KID trends weights are available on the HCUP-US website at
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KID releases for data years 1997, 2000, 2003, 2006, 2009, 2012, 2016, and 2019 are available for purchase online through the Online HCUP Central Distributor.

All HCUP data users, including data purchasers and collaborators, must complete the online HCUP Data Use Agreement Training Tool, and must read and sign the Data Use Agreement for Nationwide Databases (PDF file, 260 KB; HTML).

Questions about purchasing databases can be directed to the HCUP Central Distributor:Questions about purchasing databases can be directed to the HCUP Central Distributor: Return to Contents

The KID Database is distributed as fixed-width ASCII-formatted data files delivered via secure digital download from the Online HCUP Central Distributor. The files are compressed and encrypted with SecureZIP® from PKWARE. To load and analyze the KID data on a computer, users will need the following:

  • The password provided by the HCUP Central Distributor
  • A hard drive with at least 10 gigabytes of space available
  • A third-party zip utility such as ZIP Reader, SecureZIP®, or WinZip®, or Stuffit Expander®. (The built-in utilities in Windows® and Macintosh® cannot decompress or decrypt these zip files and will produce an error message warning of incorrect password and/or file or folder errors.)
  • SAS®, SPSS®, Stata® or similar analysis software
The data set includes weights for producing national and regional estimates. KID documentation and tools, including programs for loading the ASCII file into SAS, SPSS, or Stata (beginning with 2006), are also available on the KID Database Documentation page.

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Internet Citation: HCUP Databases. Healthcare Cost and Utilization Project (HCUP). February 2022. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 2/18/22