| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 11 |
3.7%
|
| 1989 | 1 |
0.3%
|
|
| 1999 | 5 |
1.7%
|
|
| 2000 | 3 |
1%
|
|
| 2003 | 2 |
0.7%
|
|
| 2004 | 1 |
0.3%
|
|
| 2005 | 6 |
2%
|
|
| 2006 | 6 |
2%
|
|
| 2007 | 11 |
3.7%
|
|
| 2008 | 13 |
4.3%
|
|
| 2009 | 11 |
3.7%
|
|
| 2010 | 17 |
5.7%
|
|
| 2011 | 8 |
2.7%
|
|
| 2012 | 11 |
3.7%
|
|
| 2013 | 2 |
0.7%
|
|
| 2014 | 10 |
3.3%
|
|
| 2015 | 15 |
5%
|
|
| 2016 | 24 |
8%
|
|
| 2017 | 48 |
16.1%
|
|
| 2018 | 94 |
31.4%
|
|
| Sysmiss | 301 |