| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1962 | 1 |
0.3%
|
|
| 1967 | 1 |
0.3%
|
|
| 1970 | 1 |
0.3%
|
|
| 1972 | 1 |
0.3%
|
|
| 1974 | 1 |
0.3%
|
|
| 1977 | 1 |
0.3%
|
|
| 1978 | 1 |
0.3%
|
|
| 1979 | 2 |
0.5%
|
|
| 1980 | 1 |
0.3%
|
|
| 1984 | 1 |
0.3%
|
|
| 1985 | 2 |
0.5%
|
|
| 1987 | 2 |
0.5%
|
|
| 1989 | 2 |
0.5%
|
|
| 1990 | 4 |
1.1%
|
|
| 1991 | 1 |
0.3%
|
|
| 1992 | 2 |
0.5%
|
|
| 1993 | 4 |
1.1%
|
|
| 1995 | 6 |
1.6%
|
|
| 1996 | 3 |
0.8%
|
|
| 1997 | 4 |
1.1%
|
|
| 1998 | 9 |
2.5%
|
|
| 1999 | 9 |
2.5%
|
|
| 2000 | 6 |
1.6%
|
|
| 2001 | 9 |
2.5%
|
|
| 2002 | 10 |
2.7%
|
|
| 2003 | 6 |
1.6%
|
|
| 2004 | 13 |
3.6%
|
|
| 2005 | 9 |
2.5%
|
|
| 2006 | 11 |
3%
|
|
| 2007 | 6 |
1.6%
|
|
| 2008 | 8 |
2.2%
|
|
| 2009 | 13 |
3.6%
|
|
| 2010 | 13 |
3.6%
|
|
| 2011 | 12 |
3.3%
|
|
| 2012 | 11 |
3%
|
|
| 2013 | 16 |
4.4%
|
|
| 2014 | 33 |
9.1%
|
|
| 2015 | 26 |
7.1%
|
|
| 2016 | 26 |
7.1%
|
|
| 2017 | 14 |
3.8%
|
|
| 2018 | 19 |
5.2%
|
|
| 2019 | 14 |
3.8%
|
|
| 2020 | 9 |
2.5%
|
|
| 2021 | 9 |
2.5%
|
|
| 2022 | 11 |
3%
|
|
| 2023 | 1 |
0.3%
|