| Value | Category |
|---|---|
| 1 | At least once every 12 months |
| 2 | At least once every 6 months |
| 3 | At least once every 2 months |
| 4 | At least once a month |
| 5 | Monthly |
| 6 | Never |
| 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 |