| Value | Category | Cases | |
|---|---|---|---|
| 1987 | 1 |
14.3%
|
|
| 1988 | 1 |
14.3%
|
|
| 1989 | 4 |
57.1%
|
|
| 1993 | 1 |
14.3%
|
|
| Sysmiss | 296 |