| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 10 |
6%
|
| 1985 | 2 |
1.2%
|
|
| 1989 | 1 |
0.6%
|
|
| 1990 | 1 |
0.6%
|
|
| 1994 | 1 |
0.6%
|
|
| 1995 | 3 |
1.8%
|
|
| 1998 | 1 |
0.6%
|
|
| 2000 | 4 |
2.4%
|
|
| 2001 | 2 |
1.2%
|
|
| 2004 | 1 |
0.6%
|
|
| 2005 | 1 |
0.6%
|
|
| 2007 | 6 |
3.6%
|
|
| 2008 | 4 |
2.4%
|
|
| 2009 | 3 |
1.8%
|
|
| 2010 | 5 |
3%
|
|
| 2011 | 4 |
2.4%
|
|
| 2012 | 8 |
4.8%
|
|
| 2013 | 9 |
5.4%
|
|
| 2014 | 4 |
2.4%
|
|
| 2015 | 12 |
7.2%
|
|
| 2016 | 17 |
10.2%
|
|
| 2017 | 29 |
17.4%
|
|
| 2018 | 39 |
23.4%
|
|
| Sysmiss | 73 |