| Variable | Year | Supplement |
|---|---|---|
| INCGRP | 2006 | Family file |
| INCGRP | 2005 | Family file |
| INCGRP | 2004 | Family file |
| INCGRP | 2003 | Person (core questionnaire) |
| INCGRP | 2002 | Person (core questionnaire) |
| INCGRP | 2001 | Person (core questionnaire) |
| INCGRP | 2000 | Person (core questionnaire) |
| INCGRP | 1999 | Person (core questionnaire) |
| INCGRP | 1998 | Person (core questionnaire) |
| INCGRP | 1997 | Person (core questionnaire) |