| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
1%
|
| 1998 | 1 |
0.5%
|
|
| 2003 | 1 |
0.5%
|
|
| 2005 | 1 |
0.5%
|
|
| 2008 | 1 |
0.5%
|
|
| 2010 | 3 |
1.5%
|
|
| 2011 | 3 |
1.5%
|
|
| 2012 | 7 |
3.6%
|
|
| 2013 | 10 |
5.2%
|
|
| 2014 | 20 |
10.3%
|
|
| 2015 | 17 |
8.8%
|
|
| 2016 | 28 |
14.4%
|
|
| 2017 | 23 |
11.9%
|
|
| 2018 | 77 |
39.7%
|
|
| Sysmiss | 338 |