| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 5 |
13.5%
|
| 1970 | 1 |
2.7%
|
|
| 1978 | 1 |
2.7%
|
|
| 1985 | 1 |
2.7%
|
|
| 1994 | 1 |
2.7%
|
|
| 1998 | 1 |
2.7%
|
|
| 2000 | 6 |
16.2%
|
|
| 2001 | 1 |
2.7%
|
|
| 2002 | 1 |
2.7%
|
|
| 2003 | 1 |
2.7%
|
|
| 2004 | 2 |
5.4%
|
|
| 2005 | 1 |
2.7%
|
|
| 2006 | 1 |
2.7%
|
|
| 2009 | 1 |
2.7%
|
|
| 2010 | 3 |
8.1%
|
|
| 2011 | 1 |
2.7%
|
|
| 2012 | 1 |
2.7%
|
|
| 2013 | 1 |
2.7%
|
|
| 2014 | 3 |
8.1%
|
|
| 2016 | 1 |
2.7%
|
|
| 2017 | 3 |
8.1%
|
|
| Sysmiss | 196 |