| Value | Category | Cases | |
|---|---|---|---|
| 1988 | 2 |
1.2%
|
|
| 1989 | 1 |
0.6%
|
|
| 1990 | 1 |
0.6%
|
|
| 1991 | 9 |
5.5%
|
|
| 1992 | 28 |
17.1%
|
|
| 1993 | 43 |
26.2%
|
|
| 1994 | 29 |
17.7%
|
|
| 1995 | 34 |
20.7%
|
|
| 1996 | 17 |
10.4%
|
|
| Sysmiss | 13 |