| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 8 |
0.6%
|
| 1830 | 1 |
0.1%
|
|
| 1836 | 1 |
0.1%
|
|
| 1860 | 1 |
0.1%
|
|
| 1886 | 1 |
0.1%
|
|
| 1900 | 1 |
0.1%
|
|
| 1907 | 3 |
0.2%
|
|
| 1908 | 1 |
0.1%
|
|
| 1910 | 1 |
0.1%
|
|
| 1912 | 1 |
0.1%
|
|
| 1916 | 4 |
0.3%
|
|
| 1917 | 2 |
0.1%
|
|
| 1921 | 1 |
0.1%
|
|
| 1922 | 1 |
0.1%
|
|
| 1925 | 6 |
0.4%
|
|
| 1930 | 3 |
0.2%
|
|
| 1931 | 1 |
0.1%
|
|
| 1932 | 1 |
0.1%
|
|
| 1933 | 3 |
0.2%
|
|
| 1934 | 2 |
0.1%
|
|
| 1936 | 5 |
0.4%
|
|
| 1937 | 1 |
0.1%
|
|
| 1938 | 1 |
0.1%
|
|
| 1939 | 4 |
0.3%
|
|
| 1940 | 2 |
0.1%
|
|
| 1942 | 3 |
0.2%
|
|
| 1943 | 1 |
0.1%
|
|
| 1944 | 3 |
0.2%
|
|
| 1945 | 4 |
0.3%
|
|
| 1946 | 4 |
0.3%
|
|
| 1947 | 4 |
0.3%
|
|
| 1948 | 3 |
0.2%
|
|
| 1949 | 3 |
0.2%
|
|
| 1950 | 4 |
0.3%
|
|
| 1951 | 4 |
0.3%
|
|
| 1952 | 6 |
0.4%
|
|
| 1953 | 4 |
0.3%
|
|
| 1955 | 2 |
0.1%
|
|
| 1956 | 3 |
0.2%
|
|
| 1957 | 2 |
0.1%
|
|
| 1958 | 8 |
0.6%
|
|
| 1959 | 3 |
0.2%
|
|
| 1960 | 7 |
0.5%
|
|
| 1961 | 9 |
0.7%
|
|
| 1962 | 4 |
0.3%
|
|
| 1963 | 8 |
0.6%
|
|
| 1964 | 15 |
1.1%
|
|
| 1965 | 12 |
0.9%
|
|
| 1966 | 7 |
0.5%
|
|
| 1967 | 10 |
0.7%
|
|
| 1968 | 8 |
0.6%
|
|
| 1969 | 8 |
0.6%
|
|
| 1970 | 20 |
1.5%
|
|
| 1971 | 7 |
0.5%
|
|
| 1972 | 13 |
1%
|
|
| 1973 | 12 |
0.9%
|
|
| 1974 | 18 |
1.3%
|
|
| 1975 | 12 |
0.9%
|
|
| 1976 | 24 |
1.8%
|
|
| 1977 | 17 |
1.3%
|
|
| 1978 | 24 |
1.8%
|
|
| 1979 | 14 |
1%
|
|
| 1980 | 24 |
1.8%
|
|
| 1981 | 14 |
1%
|
|
| 1982 | 12 |
0.9%
|
|
| 1983 | 15 |
1.1%
|
|
| 1984 | 14 |
1%
|
|
| 1985 | 49 |
3.7%
|
|
| 1986 | 40 |
3%
|
|
| 1987 | 33 |
2.5%
|
|
| 1988 | 25 |
1.9%
|
|
| 1989 | 30 |
2.2%
|
|
| 1990 | 47 |
3.5%
|
|
| 1991 | 35 |
2.6%
|
|
| 1992 | 33 |
2.5%
|
|
| 1993 | 28 |
2.1%
|
|
| 1994 | 42 |
3.1%
|
|
| 1995 | 46 |
3.4%
|
|
| 1996 | 48 |
3.6%
|
|
| 1997 | 34 |
2.5%
|
|
| 1998 | 52 |
3.9%
|
|
| 1999 | 36 |
2.7%
|
|
| 2000 | 36 |
2.7%
|
|
| 2001 | 41 |
3.1%
|
|
| 2002 | 49 |
3.7%
|
|
| 2003 | 34 |
2.5%
|
|
| 2004 | 24 |
1.8%
|
|
| 2005 | 21 |
1.6%
|
|
| 2006 | 7 |
0.5%
|
|
| 2007 | 8 |
0.6%
|
|
| 2008 | 9 |
0.7%
|
|
| 2009 | 11 |
0.8%
|
|
| 2010 | 13 |
1%
|
|
| 2011 | 7 |
0.5%
|
|
| 2012 | 10 |
0.7%
|
|
| 2013 | 16 |
1.2%
|
|
| 2014 | 16 |
1.2%
|
|
| 2015 | 14 |
1%
|
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