| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 1988 | 1 |
5.9%
|
|
| 1998 | 1 |
5.9%
|
|
| 2000 | 2 |
11.8%
|
|
| 2003 | 1 |
5.9%
|
|
| 2008 | 1 |
5.9%
|
|
| 2009 | 2 |
11.8%
|
|
| 2010 | 1 |
5.9%
|
|
| 2011 | 1 |
5.9%
|
|
| 2012 | 1 |
5.9%
|
|
| 2015 | 1 |
5.9%
|
|
| 2017 | 2 |
11.8%
|
|
| 2018 | 2 |
11.8%
|
|
| 2020 | 1 |
5.9%
|
|
| Sysmiss | 385 |