| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 60 |
42.3%
|
| 1972 | 1 |
0.7%
|
|
| 1999 | 1 |
0.7%
|
|
| 2002 | 2 |
1.4%
|
|
| 2003 | 1 |
0.7%
|
|
| 2005 | 2 |
1.4%
|
|
| 2006 | 7 |
4.9%
|
|
| 2007 | 2 |
1.4%
|
|
| 2009 | 1 |
0.7%
|
|
| 2010 | 3 |
2.1%
|
|
| 2011 | 3 |
2.1%
|
|
| 2012 | 4 |
2.8%
|
|
| 2013 | 4 |
2.8%
|
|
| 2014 | 10 |
7%
|
|
| 2015 | 19 |
13.4%
|
|
| 2016 | 10 |
7%
|
|
| 2017 | 8 |
5.6%
|
|
| 2018 | 4 |
2.8%
|
|
| Sysmiss | 129 |