| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 38 |
9.4%
|
| 1936 | 1 |
0.2%
|
|
| 1950 | 1 |
0.2%
|
|
| 1953 | 2 |
0.5%
|
|
| 1957 | 1 |
0.2%
|
|
| 1960 | 1 |
0.2%
|
|
| 1970 | 3 |
0.7%
|
|
| 1974 | 2 |
0.5%
|
|
| 1975 | 2 |
0.5%
|
|
| 1976 | 1 |
0.2%
|
|
| 1978 | 2 |
0.5%
|
|
| 1980 | 1 |
0.2%
|
|
| 1982 | 1 |
0.2%
|
|
| 1986 | 1 |
0.2%
|
|
| 1987 | 2 |
0.5%
|
|
| 1988 | 1 |
0.2%
|
|
| 1989 | 1 |
0.2%
|
|
| 1990 | 3 |
0.7%
|
|
| 1991 | 7 |
1.7%
|
|
| 1992 | 12 |
3%
|
|
| 1993 | 7 |
1.7%
|
|
| 1994 | 14 |
3.4%
|
|
| 1995 | 16 |
3.9%
|
|
| 1996 | 14 |
3.4%
|
|
| 1997 | 9 |
2.2%
|
|
| 1998 | 19 |
4.7%
|
|
| 1999 | 12 |
3%
|
|
| 2000 | 20 |
4.9%
|
|
| 2001 | 21 |
5.2%
|
|
| 2002 | 13 |
3.2%
|
|
| 2003 | 16 |
3.9%
|
|
| 2004 | 18 |
4.4%
|
|
| 2005 | 25 |
6.2%
|
|
| 2006 | 31 |
7.6%
|
|
| 2007 | 18 |
4.4%
|
|
| 2008 | 15 |
3.7%
|
|
| 2009 | 10 |
2.5%
|
|
| 2010 | 16 |
3.9%
|
|
| 2011 | 8 |
2%
|
|
| 2012 | 3 |
0.7%
|
|
| 2013 | 3 |
0.7%
|
|
| 2014 | 2 |
0.5%
|
|
| 2015 | 4 |
1%
|
|
| 2016 | 7 |
1.7%
|
|
| 2017 | 2 |
0.5%
|
|
| Sysmiss | 680 |