| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 40 |
14.7%
|
| 1927 | 1 |
0.4%
|
|
| 1956 | 1 |
0.4%
|
|
| 1965 | 2 |
0.7%
|
|
| 1971 | 1 |
0.4%
|
|
| 1975 | 1 |
0.4%
|
|
| 1977 | 1 |
0.4%
|
|
| 1980 | 1 |
0.4%
|
|
| 1989 | 3 |
1.1%
|
|
| 1990 | 1 |
0.4%
|
|
| 1991 | 1 |
0.4%
|
|
| 1992 | 7 |
2.6%
|
|
| 1993 | 2 |
0.7%
|
|
| 1994 | 3 |
1.1%
|
|
| 1995 | 8 |
2.9%
|
|
| 1996 | 2 |
0.7%
|
|
| 1997 | 7 |
2.6%
|
|
| 1998 | 2 |
0.7%
|
|
| 1999 | 9 |
3.3%
|
|
| 2000 | 15 |
5.5%
|
|
| 2001 | 6 |
2.2%
|
|
| 2002 | 6 |
2.2%
|
|
| 2003 | 6 |
2.2%
|
|
| 2004 | 6 |
2.2%
|
|
| 2005 | 9 |
3.3%
|
|
| 2006 | 5 |
1.8%
|
|
| 2007 | 10 |
3.7%
|
|
| 2008 | 13 |
4.8%
|
|
| 2009 | 13 |
4.8%
|
|
| 2010 | 23 |
8.5%
|
|
| 2011 | 11 |
4%
|
|
| 2012 | 11 |
4%
|
|
| 2013 | 13 |
4.8%
|
|
| 2014 | 11 |
4%
|
|
| 2015 | 10 |
3.7%
|
|
| 2016 | 6 |
2.2%
|
|
| 2017 | 3 |
1.1%
|
|
| 2018 | 2 |
0.7%
|
|
| Sysmiss | 500 |