| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.2%
|
| 1952 | 1 |
0.2%
|
|
| 1969 | 1 |
0.2%
|
|
| 1972 | 2 |
0.5%
|
|
| 1973 | 2 |
0.5%
|
|
| 1974 | 1 |
0.2%
|
|
| 1977 | 1 |
0.2%
|
|
| 1979 | 1 |
0.2%
|
|
| 1990 | 5 |
1.2%
|
|
| 1991 | 5 |
1.2%
|
|
| 1992 | 3 |
0.7%
|
|
| 1993 | 4 |
0.9%
|
|
| 1994 | 4 |
0.9%
|
|
| 1995 | 3 |
0.7%
|
|
| 1996 | 4 |
0.9%
|
|
| 1997 | 5 |
1.2%
|
|
| 1998 | 6 |
1.4%
|
|
| 1999 | 5 |
1.2%
|
|
| 2000 | 11 |
2.6%
|
|
| 2001 | 5 |
1.2%
|
|
| 2002 | 5 |
1.2%
|
|
| 2003 | 9 |
2.1%
|
|
| 2004 | 12 |
2.8%
|
|
| 2005 | 13 |
3%
|
|
| 2006 | 13 |
3%
|
|
| 2007 | 10 |
2.3%
|
|
| 2008 | 25 |
5.8%
|
|
| 2009 | 13 |
3%
|
|
| 2010 | 22 |
5.1%
|
|
| 2011 | 14 |
3.3%
|
|
| 2012 | 35 |
8.1%
|
|
| 2013 | 17 |
4%
|
|
| 2014 | 40 |
9.3%
|
|
| 2015 | 21 |
4.9%
|
|
| 2016 | 20 |
4.7%
|
|
| 2017 | 23 |
5.3%
|
|
| 2018 | 28 |
6.5%
|
|
| 2019 | 24 |
5.6%
|
|
| 2020 | 6 |
1.4%
|
|
| 2021 | 7 |
1.6%
|
|
| 2022 | 3 |
0.7%
|