| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 6 |
7.3%
|
| 1993 | 1 |
1.2%
|
|
| 1996 | 1 |
1.2%
|
|
| 1998 | 1 |
1.2%
|
|
| 2002 | 1 |
1.2%
|
|
| 2003 | 1 |
1.2%
|
|
| 2004 | 1 |
1.2%
|
|
| 2005 | 3 |
3.7%
|
|
| 2008 | 1 |
1.2%
|
|
| 2009 | 1 |
1.2%
|
|
| 2010 | 2 |
2.4%
|
|
| 2011 | 2 |
2.4%
|
|
| 2012 | 2 |
2.4%
|
|
| 2013 | 3 |
3.7%
|
|
| 2014 | 6 |
7.3%
|
|
| 2015 | 9 |
11%
|
|
| 2016 | 18 |
22%
|
|
| 2017 | 14 |
17.1%
|
|
| 2018 | 9 |
11%
|
|
| Sysmiss | 151 |