| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 1 |
0.3%
|
| 1876 | 1 |
0.3%
|
|
| 1904 | 1 |
0.3%
|
|
| 1909 | 1 |
0.3%
|
|
| 1919 | 1 |
0.3%
|
|
| 1932 | 1 |
0.3%
|
|
| 1945 | 1 |
0.3%
|
|
| 1947 | 1 |
0.3%
|
|
| 1959 | 1 |
0.3%
|
|
| 1960 | 1 |
0.3%
|
|
| 1986 | 1 |
0.3%
|
|
| 1988 | 1 |
0.3%
|
|
| 1989 | 2 |
0.6%
|
|
| 1990 | 3 |
0.8%
|
|
| 1991 | 21 |
5.8%
|
|
| 1992 | 30 |
8.3%
|
|
| 1993 | 21 |
5.8%
|
|
| 1994 | 12 |
3.3%
|
|
| 1995 | 14 |
3.9%
|
|
| 1996 | 18 |
5%
|
|
| 1997 | 18 |
5%
|
|
| 1998 | 8 |
2.2%
|
|
| 1999 | 9 |
2.5%
|
|
| 2000 | 18 |
5%
|
|
| 2001 | 9 |
2.5%
|
|
| 2002 | 9 |
2.5%
|
|
| 2003 | 12 |
3.3%
|
|
| 2004 | 14 |
3.9%
|
|
| 2005 | 12 |
3.3%
|
|
| 2006 | 12 |
3.3%
|
|
| 2007 | 8 |
2.2%
|
|
| 2008 | 7 |
1.9%
|
|
| 2009 | 11 |
3.1%
|
|
| 2010 | 13 |
3.6%
|
|
| 2011 | 16 |
4.4%
|
|
| 2012 | 7 |
1.9%
|
|
| 2013 | 5 |
1.4%
|
|
| 2014 | 8 |
2.2%
|
|
| 2015 | 9 |
2.5%
|
|
| 2016 | 9 |
2.5%
|
|
| 2017 | 5 |
1.4%
|
|
| 2018 | 1 |
0.3%
|
|
| 2019 | 5 |
1.4%
|
|
| 2020 | 2 |
0.6%
|