| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1963 | 1 |
1.7%
|
|
| 1970 | 1 |
1.7%
|
|
| 1972 | 1 |
1.7%
|
|
| 1983 | 1 |
1.7%
|
|
| 1987 | 1 |
1.7%
|
|
| 1990 | 2 |
3.4%
|
|
| 1991 | 1 |
1.7%
|
|
| 1992 | 2 |
3.4%
|
|
| 1993 | 1 |
1.7%
|
|
| 1995 | 3 |
5.1%
|
|
| 1996 | 1 |
1.7%
|
|
| 1998 | 2 |
3.4%
|
|
| 2000 | 1 |
1.7%
|
|
| 2001 | 1 |
1.7%
|
|
| 2002 | 2 |
3.4%
|
|
| 2003 | 6 |
10.2%
|
|
| 2004 | 1 |
1.7%
|
|
| 2005 | 2 |
3.4%
|
|
| 2006 | 2 |
3.4%
|
|
| 2009 | 2 |
3.4%
|
|
| 2010 | 3 |
5.1%
|
|
| 2011 | 1 |
1.7%
|
|
| 2012 | 4 |
6.8%
|
|
| 2013 | 2 |
3.4%
|
|
| 2014 | 2 |
3.4%
|
|
| 2015 | 6 |
10.2%
|
|
| 2016 | 1 |
1.7%
|
|
| 2017 | 2 |
3.4%
|
|
| 2018 | 3 |
5.1%
|
|
| 2019 | 1 |
1.7%
|
|
| Sysmiss | 89 |