| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 10 |
15.2%
|
| 2007 | 1 |
1.5%
|
|
| 2008 | 1 |
1.5%
|
|
| 2012 | 3 |
4.5%
|
|
| 2014 | 1 |
1.5%
|
|
| 2015 | 7 |
10.6%
|
|
| 2016 | 4 |
6.1%
|
|
| 2017 | 7 |
10.6%
|
|
| 2018 | 27 |
40.9%
|
|
| 2019 | 5 |
7.6%
|
|
| Sysmiss | 286 |