| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 |
0.3%
|
| 1900 | 1 |
0.1%
|
|
| 1918 | 2 |
0.2%
|
|
| 1945 | 1 |
0.1%
|
|
| 1951 | 1 |
0.1%
|
|
| 1958 | 1 |
0.1%
|
|
| 1961 | 1 |
0.1%
|
|
| 1963 | 1 |
0.1%
|
|
| 1964 | 1 |
0.1%
|
|
| 1965 | 2 |
0.2%
|
|
| 1967 | 1 |
0.1%
|
|
| 1968 | 2 |
0.2%
|
|
| 1969 | 1 |
0.1%
|
|
| 1971 | 2 |
0.2%
|
|
| 1972 | 1 |
0.1%
|
|
| 1974 | 4 |
0.4%
|
|
| 1975 | 1 |
0.1%
|
|
| 1976 | 3 |
0.3%
|
|
| 1977 | 2 |
0.2%
|
|
| 1978 | 4 |
0.4%
|
|
| 1979 | 4 |
0.4%
|
|
| 1980 | 10 |
1%
|
|
| 1981 | 5 |
0.5%
|
|
| 1982 | 4 |
0.4%
|
|
| 1983 | 5 |
0.5%
|
|
| 1984 | 8 |
0.8%
|
|
| 1985 | 9 |
0.9%
|
|
| 1986 | 8 |
0.8%
|
|
| 1987 | 1 |
0.1%
|
|
| 1988 | 6 |
0.6%
|
|
| 1989 | 14 |
1.4%
|
|
| 1990 | 17 |
1.7%
|
|
| 1991 | 15 |
1.5%
|
|
| 1992 | 9 |
0.9%
|
|
| 1993 | 17 |
1.7%
|
|
| 1994 | 10 |
1%
|
|
| 1995 | 26 |
2.7%
|
|
| 1996 | 16 |
1.6%
|
|
| 1997 | 19 |
1.9%
|
|
| 1998 | 15 |
1.5%
|
|
| 1999 | 14 |
1.4%
|
|
| 2000 | 32 |
3.3%
|
|
| 2001 | 32 |
3.3%
|
|
| 2002 | 20 |
2%
|
|
| 2003 | 17 |
1.7%
|
|
| 2004 | 18 |
1.8%
|
|
| 2005 | 21 |
2.1%
|
|
| 2006 | 22 |
2.2%
|
|
| 2007 | 30 |
3.1%
|
|
| 2008 | 32 |
3.3%
|
|
| 2009 | 32 |
3.3%
|
|
| 2010 | 39 |
4%
|
|
| 2011 | 34 |
3.5%
|
|
| 2012 | 41 |
4.2%
|
|
| 2013 | 27 |
2.8%
|
|
| 2014 | 34 |
3.5%
|
|
| 2015 | 50 |
5.1%
|
|
| 2016 | 46 |
4.7%
|
|
| 2017 | 37 |
3.8%
|
|
| 2018 | 38 |
3.9%
|
|
| 2019 | 48 |
4.9%
|
|
| 2020 | 20 |
2%
|
|
| 2021 | 26 |
2.7%
|
|
| 2022 | 10 |
1%
|
|
| 2023 | 3 |
0.3%
|
|
| 2024 | 3 |
0.3%
|