The National (Nationwide) Inpatient Sample (NIS) is part of a family of databases and software tools developed for the Healthcare Cost and Utilization Project (HCUP). The NIS is the largest publicly available all-payer inpatient health care database in the United States, yielding national estimates of hospital inpatient stays. Unweighted, it contains data from more than 7 million hospital stays each year. Weighted, it estimates more than 36 million hospitalizations nationally.
Beginning in 2012, the NIS was redesigned. It was formerly a sample of hospitals, and all discharges from those hospitals were retained.
The new NIS starting with 2012 data is a sample of discharges from all hospitals participating in HCUP.
Developed through a Federal-State-Industry partnership sponsored by the Agency for Healthcare Research and Quality (AHRQ), HCUP data inform decisionmaking at the national, State, and community levels.