| Value | Category | Cases | |
|---|---|---|---|
| 1986 | 1 |
3.1%
|
|
| 1987 | 3 |
9.4%
|
|
| 1988 | 24 |
75%
|
|
| 1989 | 4 |
12.5%
|
|
| Sysmiss | 279 |