| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
0.6%
|
| 1922 | 1 |
0.3%
|
|
| 1923 | 1 |
0.3%
|
|
| 1924 | 1 |
0.3%
|
|
| 1947 | 1 |
0.3%
|
|
| 1948 | 1 |
0.3%
|
|
| 1949 | 1 |
0.3%
|
|
| 1952 | 2 |
0.6%
|
|
| 1953 | 1 |
0.3%
|
|
| 1955 | 1 |
0.3%
|
|
| 1956 | 1 |
0.3%
|
|
| 1961 | 1 |
0.3%
|
|
| 1966 | 1 |
0.3%
|
|
| 1973 | 1 |
0.3%
|
|
| 1975 | 2 |
0.6%
|
|
| 1982 | 1 |
0.3%
|
|
| 1983 | 4 |
1.1%
|
|
| 1984 | 1 |
0.3%
|
|
| 1985 | 1 |
0.3%
|
|
| 1988 | 1 |
0.3%
|
|
| 1989 | 5 |
1.4%
|
|
| 1990 | 15 |
4.2%
|
|
| 1991 | 21 |
5.9%
|
|
| 1992 | 16 |
4.5%
|
|
| 1993 | 16 |
4.5%
|
|
| 1994 | 14 |
4%
|
|
| 1995 | 13 |
3.7%
|
|
| 1996 | 7 |
2%
|
|
| 1997 | 8 |
2.3%
|
|
| 1998 | 13 |
3.7%
|
|
| 1999 | 18 |
5.1%
|
|
| 2000 | 13 |
3.7%
|
|
| 2001 | 14 |
4%
|
|
| 2002 | 11 |
3.1%
|
|
| 2003 | 14 |
4%
|
|
| 2004 | 8 |
2.3%
|
|
| 2005 | 9 |
2.5%
|
|
| 2006 | 16 |
4.5%
|
|
| 2007 | 10 |
2.8%
|
|
| 2008 | 11 |
3.1%
|
|
| 2009 | 9 |
2.5%
|
|
| 2010 | 10 |
2.8%
|
|
| 2011 | 6 |
1.7%
|
|
| 2012 | 9 |
2.5%
|
|
| 2013 | 5 |
1.4%
|
|
| 2014 | 13 |
3.7%
|
|
| 2015 | 6 |
1.7%
|
|
| 2016 | 4 |
1.1%
|
|
| 2017 | 8 |
2.3%
|
|
| 2019 | 3 |
0.8%
|
|
| 2020 | 2 |
0.6%
|
|
| 2022 | 1 |
0.3%
|