| Value | Category | 
|---|---|
| 1 | Month and year | 
| 2 | Month and age, year imputed | 
| 3 | Year and age, month imputed | 
| 4 | Year and age, year ignored | 
| 5 | Year only, age and month imputed | 
| 6 | Age only, year and month imputed | 
| 7 | Month only, age and year imputed | 
| 8 | Season and year | 
| 9 | None reported, all imputed | 
| var_concept.title | Vocabulary | 
|---|---|
| Core demographic Variables -- TOPICS | IPUMS |