| Value | Category |
|---|---|
| -97 | Declined |
| -77 | Other |
| 1 | Ethnicity / Language |
| 2 | Religion |
| 3 | Class / Occupation |
| 4 | Gender |
| 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 |