| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 6 |
18.2%
|
| 1968 | 1 |
3%
|
|
| 2001 | 1 |
3%
|
|
| 2002 | 2 |
6.1%
|
|
| 2004 | 1 |
3%
|
|
| 2007 | 2 |
6.1%
|
|
| 2008 | 4 |
12.1%
|
|
| 2009 | 1 |
3%
|
|
| 2010 | 1 |
3%
|
|
| 2011 | 1 |
3%
|
|
| 2013 | 1 |
3%
|
|
| 2014 | 2 |
6.1%
|
|
| 2015 | 1 |
3%
|
|
| 2016 | 2 |
6.1%
|
|
| 2018 | 2 |
6.1%
|
|
| 2019 | 5 |
15.2%
|
|
| Sysmiss | 478 |