| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 |
3.7%
|
| 1987 | 1 |
0.9%
|
|
| 1997 | 1 |
0.9%
|
|
| 1998 | 1 |
0.9%
|
|
| 2000 | 3 |
2.8%
|
|
| 2001 | 1 |
0.9%
|
|
| 2003 | 3 |
2.8%
|
|
| 2004 | 1 |
0.9%
|
|
| 2005 | 1 |
0.9%
|
|
| 2006 | 4 |
3.7%
|
|
| 2007 | 3 |
2.8%
|
|
| 2008 | 3 |
2.8%
|
|
| 2009 | 3 |
2.8%
|
|
| 2010 | 5 |
4.6%
|
|
| 2011 | 5 |
4.6%
|
|
| 2012 | 4 |
3.7%
|
|
| 2013 | 2 |
1.8%
|
|
| 2014 | 11 |
10.1%
|
|
| 2015 | 14 |
12.8%
|
|
| 2016 | 11 |
10.1%
|
|
| 2017 | 16 |
14.7%
|
|
| 2018 | 11 |
10.1%
|
|
| 2019 | 1 |
0.9%
|
|
| Sysmiss | 11 |