| Value | Category | Cases | |
|---|---|---|---|
| 1987 | 1 |
7.7%
|
|
| 1989 | 1 |
7.7%
|
|
| 1990 | 1 |
7.7%
|
|
| 1992 | 1 |
7.7%
|
|
| 2005 | 2 |
15.4%
|
|
| 2008 | 1 |
7.7%
|
|
| 9999 | Do not know | 6 |
46.2%
|
| Sysmiss | 2823 |