| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 2018 | 1 |
20%
|
|
| 2019 | 2 |
40%
|
|
| 2020 | 2 |
40%
|
|
| Sysmiss | 235 |