| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 2 |
1.3%
|
| 1924 | 1 |
0.7%
|
|
| 1934 | 1 |
0.7%
|
|
| 1948 | 1 |
0.7%
|
|
| 1949 | 1 |
0.7%
|
|
| 1950 | 1 |
0.7%
|
|
| 1956 | 1 |
0.7%
|
|
| 1960 | 1 |
0.7%
|
|
| 1968 | 2 |
1.3%
|
|
| 1970 | 1 |
0.7%
|
|
| 1977 | 3 |
2%
|
|
| 1979 | 1 |
0.7%
|
|
| 1983 | 1 |
0.7%
|
|
| 1985 | 1 |
0.7%
|
|
| 1987 | 1 |
0.7%
|
|
| 1988 | 1 |
0.7%
|
|
| 1991 | 2 |
1.3%
|
|
| 1992 | 1 |
0.7%
|
|
| 1994 | 3 |
2%
|
|
| 1995 | 3 |
2%
|
|
| 1997 | 2 |
1.3%
|
|
| 1998 | 2 |
1.3%
|
|
| 1999 | 5 |
3.4%
|
|
| 2000 | 1 |
0.7%
|
|
| 2001 | 3 |
2%
|
|
| 2003 | 1 |
0.7%
|
|
| 2004 | 3 |
2%
|
|
| 2005 | 5 |
3.4%
|
|
| 2006 | 3 |
2%
|
|
| 2007 | 8 |
5.4%
|
|
| 2008 | 6 |
4%
|
|
| 2009 | 4 |
2.7%
|
|
| 2010 | 1 |
0.7%
|
|
| 2011 | 2 |
1.3%
|
|
| 2012 | 9 |
6%
|
|
| 2013 | 4 |
2.7%
|
|
| 2014 | 6 |
4%
|
|
| 2015 | 15 |
10.1%
|
|
| 2016 | 6 |
4%
|
|
| 2017 | 19 |
12.8%
|
|
| 2018 | 13 |
8.7%
|
|
| 2019 | 2 |
1.3%
|