| Value | Category |
|---|---|
| 1 | Less than 1 month |
| 2 | 1 month to < 3 months |
| 3 | 3 months to < 6 months |
| 4 | 6 months to < 12 months |
| 5 | More than 12 months |
| a | Don't know |
| b | Refused to answer |
| c | Outlier set to missing |
| d | Dropped during anonymization (available on request) |
| e | Skipped in error |
| m | Not available in wave |
| z | Not applicable |