| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
3.6%
|
| 1981 | 1 |
3.6%
|
|
| 1983 | 1 |
3.6%
|
|
| 1989 | 1 |
3.6%
|
|
| 1992 | 1 |
3.6%
|
|
| 1996 | 1 |
3.6%
|
|
| 1999 | 2 |
7.1%
|
|
| 2000 | 1 |
3.6%
|
|
| 2002 | 2 |
7.1%
|
|
| 2003 | 1 |
3.6%
|
|
| 2004 | 2 |
7.1%
|
|
| 2005 | 3 |
10.7%
|
|
| 2006 | 1 |
3.6%
|
|
| 2007 | 1 |
3.6%
|
|
| 2010 | 1 |
3.6%
|
|
| 2012 | 2 |
7.1%
|
|
| 2013 | 2 |
7.1%
|
|
| 2015 | 2 |
7.1%
|
|
| 2016 | 1 |
3.6%
|
|
| 2017 | 1 |
3.6%
|
|
| Sysmiss | 92 |