| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1982 | 1 |
0.4%
|
|
| 1987 | 1 |
0.4%
|
|
| 1992 | 1 |
0.4%
|
|
| 1993 | 2 |
0.8%
|
|
| 1994 | 2 |
0.8%
|
|
| 1995 | 2 |
0.8%
|
|
| 1997 | 2 |
0.8%
|
|
| 1998 | 3 |
1.2%
|
|
| 1999 | 5 |
2%
|
|
| 2000 | 14 |
5.6%
|
|
| 2001 | 2 |
0.8%
|
|
| 2002 | 3 |
1.2%
|
|
| 2003 | 3 |
1.2%
|
|
| 2004 | 6 |
2.4%
|
|
| 2005 | 7 |
2.8%
|
|
| 2006 | 6 |
2.4%
|
|
| 2007 | 3 |
1.2%
|
|
| 2008 | 4 |
1.6%
|
|
| 2009 | 11 |
4.4%
|
|
| 2010 | 18 |
7.2%
|
|
| 2011 | 10 |
4%
|
|
| 2012 | 10 |
4%
|
|
| 2013 | 21 |
8.4%
|
|
| 2014 | 29 |
11.6%
|
|
| 2015 | 34 |
13.6%
|
|
| 2016 | 33 |
13.2%
|
|
| 2017 | 11 |
4.4%
|
|
| 2018 | 4 |
1.6%
|
|
| 2019 | 2 |
0.8%
|