| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 7 |
10%
|
| 2009 | 2 |
2.9%
|
|
| 2010 | 1 |
1.4%
|
|
| 2014 | 1 |
1.4%
|
|
| 2015 | 3 |
4.3%
|
|
| 2016 | 9 |
12.9%
|
|
| 2017 | 12 |
17.1%
|
|
| 2018 | 35 |
50%
|
|
| Sysmiss | 50 |