| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.3%
|
| 1937 | 1 |
0.3%
|
|
| 1954 | 1 |
0.3%
|
|
| 1957 | 1 |
0.3%
|
|
| 1958 | 1 |
0.3%
|
|
| 1972 | 1 |
0.3%
|
|
| 1973 | 3 |
0.8%
|
|
| 1975 | 1 |
0.3%
|
|
| 1976 | 2 |
0.6%
|
|
| 1978 | 1 |
0.3%
|
|
| 1979 | 2 |
0.6%
|
|
| 1982 | 2 |
0.6%
|
|
| 1983 | 2 |
0.6%
|
|
| 1984 | 1 |
0.3%
|
|
| 1986 | 1 |
0.3%
|
|
| 1988 | 1 |
0.3%
|
|
| 1993 | 1 |
0.3%
|
|
| 1996 | 2 |
0.6%
|
|
| 1997 | 1 |
0.3%
|
|
| 1998 | 7 |
2%
|
|
| 1999 | 1 |
0.3%
|
|
| 2000 | 4 |
1.1%
|
|
| 2002 | 3 |
0.8%
|
|
| 2003 | 5 |
1.4%
|
|
| 2004 | 2 |
0.6%
|
|
| 2005 | 6 |
1.7%
|
|
| 2006 | 11 |
3.1%
|
|
| 2007 | 8 |
2.2%
|
|
| 2008 | 16 |
4.5%
|
|
| 2009 | 6 |
1.7%
|
|
| 2010 | 16 |
4.5%
|
|
| 2011 | 15 |
4.2%
|
|
| 2012 | 15 |
4.2%
|
|
| 2013 | 18 |
5%
|
|
| 2014 | 21 |
5.9%
|
|
| 2015 | 32 |
8.9%
|
|
| 2016 | 26 |
7.3%
|
|
| 2017 | 28 |
7.8%
|
|
| 2018 | 25 |
7%
|
|
| 2019 | 18 |
5%
|
|
| 2020 | 13 |
3.6%
|
|
| 2021 | 14 |
3.9%
|
|
| 2022 | 22 |
6.1%
|