| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 |
0.4%
|
| 1960 | 2 |
0.2%
|
|
| 1961 | 1 |
0.1%
|
|
| 1962 | 1 |
0.1%
|
|
| 1963 | 2 |
0.2%
|
|
| 1964 | 1 |
0.1%
|
|
| 1965 | 1 |
0.1%
|
|
| 1968 | 1 |
0.1%
|
|
| 1970 | 3 |
0.3%
|
|
| 1971 | 1 |
0.1%
|
|
| 1974 | 1 |
0.1%
|
|
| 1977 | 1 |
0.1%
|
|
| 1979 | 4 |
0.4%
|
|
| 1980 | 5 |
0.5%
|
|
| 1981 | 2 |
0.2%
|
|
| 1982 | 6 |
0.6%
|
|
| 1983 | 1 |
0.1%
|
|
| 1984 | 2 |
0.2%
|
|
| 1985 | 3 |
0.3%
|
|
| 1986 | 2 |
0.2%
|
|
| 1987 | 3 |
0.3%
|
|
| 1988 | 5 |
0.5%
|
|
| 1989 | 1 |
0.1%
|
|
| 1990 | 16 |
1.6%
|
|
| 1991 | 4 |
0.4%
|
|
| 1992 | 5 |
0.5%
|
|
| 1993 | 9 |
0.9%
|
|
| 1994 | 5 |
0.5%
|
|
| 1995 | 10 |
1%
|
|
| 1996 | 9 |
0.9%
|
|
| 1997 | 7 |
0.7%
|
|
| 1998 | 10 |
1%
|
|
| 1999 | 7 |
0.7%
|
|
| 2000 | 15 |
1.5%
|
|
| 2001 | 9 |
0.9%
|
|
| 2002 | 11 |
1.1%
|
|
| 2003 | 17 |
1.7%
|
|
| 2004 | 33 |
3.2%
|
|
| 2005 | 57 |
5.6%
|
|
| 2006 | 59 |
5.8%
|
|
| 2007 | 43 |
4.2%
|
|
| 2008 | 48 |
4.7%
|
|
| 2009 | 47 |
4.6%
|
|
| 2010 | 102 |
10%
|
|
| 2011 | 55 |
5.4%
|
|
| 2012 | 46 |
4.5%
|
|
| 2013 | 53 |
5.2%
|
|
| 2014 | 32 |
3.1%
|
|
| 2015 | 50 |
4.9%
|
|
| 2016 | 31 |
3%
|
|
| 2017 | 40 |
3.9%
|
|
| 2018 | 61 |
6%
|
|
| 2019 | 40 |
3.9%
|
|
| 2020 | 23 |
2.3%
|
|
| 2021 | 12 |
1.2%
|