This is a 7-character string variable.
For sample adults and sample children, HHX reports the person's household number on the original NHIS data. HHX is unique within sample but only unique across samples when combined with information on year. Prior to 2019, this variable was available for all persons.
The NHIS questionnaire was substantially redesigned in 2019 to introduce a different data collection structure and new content. Beginning in 2019, HHX leads with the character "H" followed by six numeric digits. Prior to 2019, HHX consisted only of six numeric digits. This does not change the fact that HHX is unique within sample. For more information on changes in terminology, universes, and data collection methods beginning in 2019, please see the user note.
- 1997-2018: All persons.
- 2019: Sample adults age 18+ and sample children age 0-17.