| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
0.5%
|
| 1936 | 1 |
0.3%
|
|
| 1941 | 1 |
0.3%
|
|
| 1948 | 1 |
0.3%
|
|
| 1950 | 1 |
0.3%
|
|
| 1958 | 1 |
0.3%
|
|
| 1960 | 1 |
0.3%
|
|
| 1964 | 2 |
0.5%
|
|
| 1965 | 1 |
0.3%
|
|
| 1966 | 1 |
0.3%
|
|
| 1968 | 1 |
0.3%
|
|
| 1969 | 1 |
0.3%
|
|
| 1970 | 2 |
0.5%
|
|
| 1973 | 1 |
0.3%
|
|
| 1974 | 1 |
0.3%
|
|
| 1975 | 1 |
0.3%
|
|
| 1978 | 2 |
0.5%
|
|
| 1980 | 2 |
0.5%
|
|
| 1983 | 3 |
0.8%
|
|
| 1984 | 2 |
0.5%
|
|
| 1985 | 3 |
0.8%
|
|
| 1986 | 1 |
0.3%
|
|
| 1987 | 2 |
0.5%
|
|
| 1988 | 2 |
0.5%
|
|
| 1989 | 3 |
0.8%
|
|
| 1990 | 2 |
0.5%
|
|
| 1991 | 3 |
0.8%
|
|
| 1992 | 2 |
0.5%
|
|
| 1993 | 2 |
0.5%
|
|
| 1994 | 1 |
0.3%
|
|
| 1995 | 2 |
0.5%
|
|
| 1996 | 5 |
1.3%
|
|
| 1997 | 2 |
0.5%
|
|
| 1998 | 11 |
2.9%
|
|
| 1999 | 5 |
1.3%
|
|
| 2000 | 15 |
3.9%
|
|
| 2001 | 5 |
1.3%
|
|
| 2002 | 5 |
1.3%
|
|
| 2003 | 5 |
1.3%
|
|
| 2004 | 8 |
2.1%
|
|
| 2005 | 15 |
3.9%
|
|
| 2006 | 12 |
3.2%
|
|
| 2007 | 11 |
2.9%
|
|
| 2008 | 16 |
4.2%
|
|
| 2009 | 10 |
2.6%
|
|
| 2010 | 21 |
5.5%
|
|
| 2011 | 18 |
4.7%
|
|
| 2012 | 19 |
5%
|
|
| 2013 | 8 |
2.1%
|
|
| 2014 | 12 |
3.2%
|
|
| 2015 | 13 |
3.4%
|
|
| 2016 | 14 |
3.7%
|
|
| 2017 | 20 |
5.3%
|
|
| 2018 | 30 |
7.9%
|
|
| 2019 | 20 |
5.3%
|
|
| 2020 | 19 |
5%
|
|
| 2021 | 4 |
1.1%
|
|
| 2022 | 5 |
1.3%
|
|
| 2023 | 1 |
0.3%
|