| Value | Category | Cases | |
|---|---|---|---|
| 99 | Missing | 1 |
1.9%
|
| 1988 | 39 |
73.6%
|
|
| 1989 | 3 |
5.7%
|
|
| 1992 | 2 |
3.8%
|
|
| 1994 | 6 |
11.3%
|
|
| 1996 | 1 |
1.9%
|
|
| 1998 | 1 |
1.9%
|
|
| Sysmiss | 1672 |