| Value | Category |
|---|---|
| 1 | Wave 1 (14/5/2020-8/7/2020) |
| 2 | Wave 2 (16/7/2020-18/9/2020) |
| 3 | Wave 3 (28/9/2020-30/11/2020) |
| 4 | Wave 4 (15/1/2021-25/3/2021) |
| 5 | Wave 5 (29/3/2021-13/6/2021) |
| 6 | Don't know |
| 7 | Refused to answer |
| 8 | Outlier set to missing |
| 9 | Inconsistency set to missing |
| 10 | Not applicable |