| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1989 | 1 |
0.3%
|
|
| 1992 | 2 |
0.6%
|
|
| 1993 | 1 |
0.3%
|
|
| 1995 | 4 |
1.3%
|
|
| 1996 | 1 |
0.3%
|
|
| 1997 | 3 |
1%
|
|
| 1998 | 5 |
1.6%
|
|
| 1999 | 4 |
1.3%
|
|
| 2000 | 2 |
0.6%
|
|
| 2001 | 4 |
1.3%
|
|
| 2002 | 4 |
1.3%
|
|
| 2003 | 3 |
1%
|
|
| 2004 | 3 |
1%
|
|
| 2005 | 3 |
1%
|
|
| 2006 | 5 |
1.6%
|
|
| 2007 | 4 |
1.3%
|
|
| 2008 | 11 |
3.5%
|
|
| 2009 | 5 |
1.6%
|
|
| 2010 | 24 |
7.7%
|
|
| 2011 | 11 |
3.5%
|
|
| 2012 | 21 |
6.8%
|
|
| 2013 | 16 |
5.1%
|
|
| 2014 | 15 |
4.8%
|
|
| 2015 | 22 |
7.1%
|
|
| 2016 | 19 |
6.1%
|
|
| 2017 | 26 |
8.4%
|
|
| 2018 | 31 |
10%
|
|
| 2019 | 23 |
7.4%
|
|
| 2020 | 17 |
5.5%
|
|
| 2021 | 16 |
5.1%
|
|
| 2022 | 4 |
1.3%
|
|
| 2023 | 1 |
0.3%
|