| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 22 |
55%
|
| 1998 | 1 |
2.5%
|
|
| 2007 | 1 |
2.5%
|
|
| 2010 | 1 |
2.5%
|
|
| 2015 | 3 |
7.5%
|
|
| 2016 | 1 |
2.5%
|
|
| 2019 | 4 |
10%
|
|
| 2020 | 3 |
7.5%
|
|
| 2021 | 4 |
10%
|
|
| Sysmiss | 1687 |