| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 39 |
10.2%
|
| 1957 | 1 |
0.3%
|
|
| 1965 | 2 |
0.5%
|
|
| 1967 | 2 |
0.5%
|
|
| 1969 | 1 |
0.3%
|
|
| 1970 | 4 |
1%
|
|
| 1971 | 1 |
0.3%
|
|
| 1972 | 4 |
1%
|
|
| 1973 | 3 |
0.8%
|
|
| 1974 | 1 |
0.3%
|
|
| 1975 | 4 |
1%
|
|
| 1977 | 2 |
0.5%
|
|
| 1978 | 1 |
0.3%
|
|
| 1979 | 3 |
0.8%
|
|
| 1980 | 6 |
1.6%
|
|
| 1981 | 2 |
0.5%
|
|
| 1982 | 1 |
0.3%
|
|
| 1983 | 1 |
0.3%
|
|
| 1984 | 5 |
1.3%
|
|
| 1985 | 6 |
1.6%
|
|
| 1986 | 4 |
1%
|
|
| 1987 | 5 |
1.3%
|
|
| 1988 | 6 |
1.6%
|
|
| 1989 | 7 |
1.8%
|
|
| 1990 | 17 |
4.5%
|
|
| 1991 | 5 |
1.3%
|
|
| 1992 | 4 |
1%
|
|
| 1993 | 6 |
1.6%
|
|
| 1994 | 5 |
1.3%
|
|
| 1995 | 18 |
4.7%
|
|
| 1996 | 5 |
1.3%
|
|
| 1997 | 7 |
1.8%
|
|
| 1998 | 9 |
2.4%
|
|
| 1999 | 10 |
2.6%
|
|
| 2000 | 17 |
4.5%
|
|
| 2001 | 4 |
1%
|
|
| 2002 | 2 |
0.5%
|
|
| 2003 | 4 |
1%
|
|
| 2004 | 9 |
2.4%
|
|
| 2005 | 7 |
1.8%
|
|
| 2006 | 6 |
1.6%
|
|
| 2007 | 9 |
2.4%
|
|
| 2008 | 7 |
1.8%
|
|
| 2009 | 10 |
2.6%
|
|
| 2010 | 11 |
2.9%
|
|
| 2011 | 3 |
0.8%
|
|
| 2012 | 4 |
1%
|
|
| 2013 | 7 |
1.8%
|
|
| 2014 | 16 |
4.2%
|
|
| 2015 | 6 |
1.6%
|
|
| 2016 | 13 |
3.4%
|
|
| 2017 | 9 |
2.4%
|
|
| 2018 | 9 |
2.4%
|
|
| 2019 | 9 |
2.4%
|
|
| 2020 | 11 |
2.9%
|
|
| 2021 | 4 |
1%
|
|
| 2022 | 1 |
0.3%
|
|
| 2023 | 5 |
1.3%
|
|
| 2024 | 1 |
0.3%
|
|
| Sysmiss | 231 |