| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
5.3%
|
| 2009 | 1 |
1.1%
|
|
| 2012 | 2 |
2.1%
|
|
| 2014 | 3 |
3.2%
|
|
| 2015 | 2 |
2.1%
|
|
| 2016 | 1 |
1.1%
|
|
| 2017 | 14 |
14.9%
|
|
| 2018 | 27 |
28.7%
|
|
| 2019 | 35 |
37.2%
|
|
| 2020 | 4 |
4.3%
|
|
| Sysmiss | 507 |