| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 39 |
2.8%
|
| 1890 | 2 |
0.1%
|
|
| 1900 | 1 |
0.1%
|
|
| 1908 | 1 |
0.1%
|
|
| 1910 | 1 |
0.1%
|
|
| 1917 | 1 |
0.1%
|
|
| 1918 | 1 |
0.1%
|
|
| 1920 | 1 |
0.1%
|
|
| 1927 | 1 |
0.1%
|
|
| 1928 | 2 |
0.1%
|
|
| 1945 | 1 |
0.1%
|
|
| 1946 | 2 |
0.1%
|
|
| 1947 | 3 |
0.2%
|
|
| 1948 | 1 |
0.1%
|
|
| 1950 | 1 |
0.1%
|
|
| 1951 | 1 |
0.1%
|
|
| 1952 | 2 |
0.1%
|
|
| 1953 | 2 |
0.1%
|
|
| 1956 | 1 |
0.1%
|
|
| 1960 | 2 |
0.1%
|
|
| 1966 | 1 |
0.1%
|
|
| 1967 | 1 |
0.1%
|
|
| 1968 | 2 |
0.1%
|
|
| 1969 | 1 |
0.1%
|
|
| 1970 | 1 |
0.1%
|
|
| 1971 | 2 |
0.1%
|
|
| 1972 | 1 |
0.1%
|
|
| 1974 | 4 |
0.3%
|
|
| 1975 | 3 |
0.2%
|
|
| 1976 | 4 |
0.3%
|
|
| 1979 | 5 |
0.4%
|
|
| 1980 | 7 |
0.5%
|
|
| 1981 | 5 |
0.4%
|
|
| 1982 | 10 |
0.7%
|
|
| 1983 | 10 |
0.7%
|
|
| 1984 | 11 |
0.8%
|
|
| 1985 | 14 |
1%
|
|
| 1986 | 13 |
0.9%
|
|
| 1987 | 12 |
0.9%
|
|
| 1988 | 13 |
0.9%
|
|
| 1989 | 43 |
3.1%
|
|
| 1990 | 53 |
3.9%
|
|
| 1991 | 58 |
4.2%
|
|
| 1992 | 54 |
3.9%
|
|
| 1993 | 40 |
2.9%
|
|
| 1994 | 37 |
2.7%
|
|
| 1995 | 46 |
3.4%
|
|
| 1996 | 43 |
3.1%
|
|
| 1997 | 40 |
2.9%
|
|
| 1998 | 42 |
3.1%
|
|
| 1999 | 43 |
3.1%
|
|
| 2000 | 65 |
4.7%
|
|
| 2001 | 75 |
5.5%
|
|
| 2002 | 65 |
4.7%
|
|
| 2003 | 47 |
3.4%
|
|
| 2004 | 38 |
2.8%
|
|
| 2005 | 64 |
4.7%
|
|
| 2006 | 27 |
2%
|
|
| 2007 | 20 |
1.5%
|
|
| 2008 | 22 |
1.6%
|
|
| 2009 | 37 |
2.7%
|
|
| 2010 | 48 |
3.5%
|
|
| 2011 | 26 |
1.9%
|
|
| 2012 | 32 |
2.3%
|
|
| 2013 | 14 |
1%
|
|
| 2014 | 25 |
1.8%
|
|
| 2015 | 22 |
1.6%
|
|
| 2016 | 21 |
1.5%
|
|
| 2017 | 36 |
2.6%
|