| Value | Category | Cases | |
|---|---|---|---|
| 2002 | 4 |
21.1%
|
|
| 2003 | 3 |
15.8%
|
|
| 2004 | 4 |
21.1%
|
|
| 2005 | 6 |
31.6%
|
|
| 2006 | 1 |
5.3%
|
|
| 9998 | DK | 0 |
0%
|
| 9999 | Missing | 1 |
5.3%
|
| Sysmiss | 173 |