| Value | Category | Cases | |
|---|---|---|---|
| 1980 | 1 |
0.5%
|
|
| 1987 | 2 |
1%
|
|
| 1994 | 46 |
23.2%
|
|
| 1995 | 16 |
8.1%
|
|
| 1996 | 22 |
11.1%
|
|
| 1997 | 111 |
56.1%
|
|
| Sysmiss | 115 |