Beginning in 1998, NIS weights calculations were changed in order to make national estimates of the number of discharges more accurate:
- Rehabilitation hospitals were excluded from the NIS hospital universe and sample.
- American Hospital Association hospital unit discharges were used instead of total facility discharges, which include nursing home unit discharges.
In order to facilitate analysis of trends using multiple years of NIS data, an alternate set of NIS discharge and hospital weights for the 1988-1997 HCUP NIS were developed. These alternative weights were calculated in the same way as the weights for the 1998 and later years of the NIS. The
NIS Trends Report includes details regarding the alternate weights and other recommendations for trends analysis. . For analyses that span multiple years, it is advisable to obtain the NIS Trends Supplemental files (NIS-Trends). These files contain the revised trend weights described below in addition to data elements that are consistently defined across data years. For more information, see
NIS Trends Supplemental Files.
The alternate weights are available as ASCII files along with SAS and SPSS load programs. Each file contains the following three data elements:
| Name |
Type |
Label |
| HOSPID |
Numeric |
HCUP hospital identification number |
| DISCWT |
Numeric |
Post-1997 weight to discharges in AHA universe |
| HOSPWT |
Numeric |
Post-1997 weight to hospitals in AHA universe |
Alternative NIS Weights files for download:
- 1988
- 1989
- 1990
- 1991
- 1992
- 1993
- 1994
- 1995
- 1996
- 1997
