| Value | Category |
|---|---|
| 0 | Month, year and day |
| 1 | Month and year - information complete |
| 2 | Month and age - year imputed |
| 3 | Year and age - month imputed |
| 4 | Year and age - year ignored |
| 5 | Year - age/month imputed |
| 6 | Age - year/month imputed |
| 7 | Month - age/year imputed |
| 8 | None - all imputed |