| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.7%
|
| 1930 | 1 |
0.7%
|
|
| 1935 | 1 |
0.7%
|
|
| 1952 | 1 |
0.7%
|
|
| 1963 | 1 |
0.7%
|
|
| 1966 | 1 |
0.7%
|
|
| 1968 | 1 |
0.7%
|
|
| 1972 | 3 |
2%
|
|
| 1973 | 1 |
0.7%
|
|
| 1974 | 1 |
0.7%
|
|
| 1975 | 4 |
2.7%
|
|
| 1977 | 1 |
0.7%
|
|
| 1978 | 1 |
0.7%
|
|
| 1979 | 2 |
1.3%
|
|
| 1980 | 1 |
0.7%
|
|
| 1981 | 3 |
2%
|
|
| 1982 | 3 |
2%
|
|
| 1983 | 1 |
0.7%
|
|
| 1984 | 1 |
0.7%
|
|
| 1985 | 1 |
0.7%
|
|
| 1986 | 1 |
0.7%
|
|
| 1989 | 3 |
2%
|
|
| 1990 | 3 |
2%
|
|
| 1991 | 2 |
1.3%
|
|
| 1992 | 4 |
2.7%
|
|
| 1994 | 1 |
0.7%
|
|
| 1995 | 1 |
0.7%
|
|
| 1996 | 3 |
2%
|
|
| 1997 | 4 |
2.7%
|
|
| 1998 | 2 |
1.3%
|
|
| 1999 | 1 |
0.7%
|
|
| 2001 | 1 |
0.7%
|
|
| 2002 | 6 |
4%
|
|
| 2003 | 2 |
1.3%
|
|
| 2004 | 2 |
1.3%
|
|
| 2005 | 3 |
2%
|
|
| 2006 | 1 |
0.7%
|
|
| 2007 | 5 |
3.3%
|
|
| 2008 | 6 |
4%
|
|
| 2009 | 3 |
2%
|
|
| 2010 | 4 |
2.7%
|
|
| 2011 | 6 |
4%
|
|
| 2012 | 5 |
3.3%
|
|
| 2013 | 3 |
2%
|
|
| 2014 | 1 |
0.7%
|
|
| 2015 | 4 |
2.7%
|
|
| 2016 | 10 |
6.7%
|
|
| 2017 | 5 |
3.3%
|
|
| 2018 | 6 |
4%
|
|
| 2019 | 5 |
3.3%
|
|
| 2020 | 7 |
4.7%
|
|
| 2021 | 7 |
4.7%
|
|
| 2022 | 1 |
0.7%
|
|
| 2023 | 2 |
1.3%
|