| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1935 | 2 |
0.2%
|
|
| 1941 | 2 |
0.2%
|
|
| 1942 | 1 |
0.1%
|
|
| 1944 | 1 |
0.1%
|
|
| 1948 | 1 |
0.1%
|
|
| 1956 | 1 |
0.1%
|
|
| 1961 | 1 |
0.1%
|
|
| 1966 | 1 |
0.1%
|
|
| 1987 | 1 |
0.1%
|
|
| 1991 | 6 |
0.6%
|
|
| 1992 | 9 |
0.9%
|
|
| 1993 | 6 |
0.6%
|
|
| 1994 | 6 |
0.6%
|
|
| 1995 | 12 |
1.2%
|
|
| 1996 | 10 |
1%
|
|
| 1997 | 18 |
1.8%
|
|
| 1998 | 28 |
2.8%
|
|
| 1999 | 24 |
2.4%
|
|
| 2000 | 18 |
1.8%
|
|
| 2001 | 22 |
2.2%
|
|
| 2002 | 28 |
2.8%
|
|
| 2003 | 36 |
3.6%
|
|
| 2004 | 47 |
4.6%
|
|
| 2005 | 40 |
3.9%
|
|
| 2006 | 36 |
3.6%
|
|
| 2007 | 36 |
3.6%
|
|
| 2008 | 33 |
3.3%
|
|
| 2009 | 36 |
3.6%
|
|
| 2010 | 39 |
3.8%
|
|
| 2011 | 43 |
4.2%
|
|
| 2012 | 25 |
2.5%
|
|
| 2013 | 38 |
3.8%
|
|
| 2014 | 53 |
5.2%
|
|
| 2015 | 45 |
4.4%
|
|
| 2016 | 49 |
4.8%
|
|
| 2017 | 53 |
5.2%
|
|
| 2018 | 33 |
3.3%
|
|
| 2019 | 32 |
3.2%
|
|
| 2020 | 29 |
2.9%
|
|
| 2021 | 41 |
4%
|
|
| 2022 | 43 |
4.2%
|
|
| 2023 | 28 |
2.8%
|