| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1988 | 1 |
0.2%
|
|
| 1990 | 3 |
0.6%
|
|
| 1991 | 2 |
0.4%
|
|
| 1992 | 2 |
0.4%
|
|
| 1993 | 2 |
0.4%
|
|
| 1994 | 3 |
0.6%
|
|
| 1995 | 5 |
1%
|
|
| 1996 | 6 |
1.2%
|
|
| 1997 | 2 |
0.4%
|
|
| 1998 | 9 |
1.7%
|
|
| 1999 | 2 |
0.4%
|
|
| 2000 | 18 |
3.5%
|
|
| 2001 | 10 |
1.9%
|
|
| 2002 | 9 |
1.7%
|
|
| 2003 | 4 |
0.8%
|
|
| 2004 | 11 |
2.1%
|
|
| 2005 | 12 |
2.3%
|
|
| 2006 | 8 |
1.5%
|
|
| 2007 | 8 |
1.5%
|
|
| 2008 | 14 |
2.7%
|
|
| 2009 | 16 |
3.1%
|
|
| 2010 | 31 |
6%
|
|
| 2011 | 8 |
1.5%
|
|
| 2012 | 26 |
5%
|
|
| 2013 | 23 |
4.4%
|
|
| 2014 | 20 |
3.9%
|
|
| 2015 | 40 |
7.7%
|
|
| 2016 | 36 |
6.9%
|
|
| 2017 | 52 |
10%
|
|
| 2018 | 74 |
14.3%
|
|
| 2019 | 43 |
8.3%
|
|
| 2020 | 18 |
3.5%
|
|
| 2021 | 1 |
0.2%
|