| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| 1874 | 1 |
0.2%
|
|
| 1878 | 1 |
0.2%
|
|
| 1893 | 1 |
0.2%
|
|
| 1905 | 1 |
0.2%
|
|
| 1907 | 1 |
0.2%
|
|
| 1912 | 1 |
0.2%
|
|
| 1921 | 4 |
0.8%
|
|
| 1925 | 1 |
0.2%
|
|
| 1929 | 1 |
0.2%
|
|
| 1941 | 1 |
0.2%
|
|
| 1944 | 1 |
0.2%
|
|
| 1946 | 1 |
0.2%
|
|
| 1947 | 1 |
0.2%
|
|
| 1950 | 1 |
0.2%
|
|
| 1951 | 1 |
0.2%
|
|
| 1953 | 1 |
0.2%
|
|
| 1954 | 2 |
0.4%
|
|
| 1956 | 2 |
0.4%
|
|
| 1957 | 1 |
0.2%
|
|
| 1958 | 1 |
0.2%
|
|
| 1960 | 1 |
0.2%
|
|
| 1965 | 2 |
0.4%
|
|
| 1971 | 2 |
0.4%
|
|
| 1972 | 1 |
0.2%
|
|
| 1974 | 2 |
0.4%
|
|
| 1975 | 1 |
0.2%
|
|
| 1977 | 1 |
0.2%
|
|
| 1980 | 1 |
0.2%
|
|
| 1983 | 1 |
0.2%
|
|
| 1985 | 2 |
0.4%
|
|
| 1987 | 1 |
0.2%
|
|
| 1988 | 2 |
0.4%
|
|
| 1989 | 4 |
0.8%
|
|
| 1990 | 19 |
4%
|
|
| 1991 | 21 |
4.4%
|
|
| 1992 | 25 |
5.3%
|
|
| 1993 | 15 |
3.2%
|
|
| 1994 | 25 |
5.3%
|
|
| 1995 | 50 |
10.5%
|
|
| 1996 | 13 |
2.7%
|
|
| 1997 | 8 |
1.7%
|
|
| 1998 | 10 |
2.1%
|
|
| 1999 | 13 |
2.7%
|
|
| 2000 | 7 |
1.5%
|
|
| 2001 | 10 |
2.1%
|
|
| 2002 | 9 |
1.9%
|
|
| 2003 | 8 |
1.7%
|
|
| 2004 | 7 |
1.5%
|
|
| 2005 | 10 |
2.1%
|
|
| 2006 | 8 |
1.7%
|
|
| 2007 | 17 |
3.6%
|
|
| 2008 | 9 |
1.9%
|
|
| 2009 | 11 |
2.3%
|
|
| 2010 | 11 |
2.3%
|
|
| 2011 | 17 |
3.6%
|
|
| 2012 | 16 |
3.4%
|
|
| 2013 | 21 |
4.4%
|
|
| 2014 | 14 |
3%
|
|
| 2015 | 12 |
2.5%
|
|
| 2016 | 11 |
2.3%
|
|
| 2017 | 5 |
1.1%
|
|
| 2018 | 8 |
1.7%
|
|
| 2019 | 6 |
1.3%
|
|
| 2020 | 6 |
1.3%
|
|
| 2021 | 5 |
1.1%
|