| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 2017 | 3 |
60%
|
|
| 2018 | 1 |
20%
|
|
| 2019 | 1 |
20%
|
|
| Sysmiss | 145 |