| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 |
0.7%
|
| 1925 | 1 |
0.2%
|
|
| 1928 | 1 |
0.2%
|
|
| 1933 | 1 |
0.2%
|
|
| 1945 | 1 |
0.2%
|
|
| 1947 | 1 |
0.2%
|
|
| 1949 | 2 |
0.5%
|
|
| 1950 | 1 |
0.2%
|
|
| 1952 | 1 |
0.2%
|
|
| 1953 | 1 |
0.2%
|
|
| 1955 | 1 |
0.2%
|
|
| 1956 | 1 |
0.2%
|
|
| 1960 | 1 |
0.2%
|
|
| 1962 | 1 |
0.2%
|
|
| 1964 | 1 |
0.2%
|
|
| 1965 | 1 |
0.2%
|
|
| 1967 | 1 |
0.2%
|
|
| 1968 | 1 |
0.2%
|
|
| 1970 | 3 |
0.7%
|
|
| 1971 | 1 |
0.2%
|
|
| 1972 | 1 |
0.2%
|
|
| 1974 | 2 |
0.5%
|
|
| 1975 | 1 |
0.2%
|
|
| 1976 | 1 |
0.2%
|
|
| 1977 | 2 |
0.5%
|
|
| 1984 | 2 |
0.5%
|
|
| 1985 | 2 |
0.5%
|
|
| 1986 | 1 |
0.2%
|
|
| 1987 | 1 |
0.2%
|
|
| 1988 | 1 |
0.2%
|
|
| 1989 | 6 |
1.5%
|
|
| 1990 | 3 |
0.7%
|
|
| 1991 | 5 |
1.2%
|
|
| 1992 | 5 |
1.2%
|
|
| 1993 | 3 |
0.7%
|
|
| 1994 | 5 |
1.2%
|
|
| 1995 | 2 |
0.5%
|
|
| 1996 | 4 |
1%
|
|
| 1997 | 7 |
1.7%
|
|
| 1998 | 15 |
3.7%
|
|
| 1999 | 3 |
0.7%
|
|
| 2000 | 22 |
5.5%
|
|
| 2001 | 4 |
1%
|
|
| 2002 | 14 |
3.5%
|
|
| 2003 | 9 |
2.2%
|
|
| 2004 | 9 |
2.2%
|
|
| 2005 | 8 |
2%
|
|
| 2006 | 7 |
1.7%
|
|
| 2007 | 12 |
3%
|
|
| 2008 | 9 |
2.2%
|
|
| 2009 | 10 |
2.5%
|
|
| 2010 | 18 |
4.5%
|
|
| 2011 | 20 |
5%
|
|
| 2012 | 14 |
3.5%
|
|
| 2013 | 14 |
3.5%
|
|
| 2014 | 13 |
3.2%
|
|
| 2015 | 14 |
3.5%
|
|
| 2016 | 21 |
5.2%
|
|
| 2017 | 23 |
5.7%
|
|
| 2018 | 18 |
4.5%
|
|
| 2019 | 25 |
6.2%
|
|
| 2020 | 16 |
4%
|
|
| 2021 | 5 |
1.2%
|