| Value | Category | Cases | |
|---|---|---|---|
| 1990 | 2 |
0.4%
|
|
| 1993 | 1 |
0.2%
|
|
| 1995 | 1 |
0.2%
|
|
| 1996 | 1 |
0.2%
|
|
| 1997 | 545 |
99.1%
|
|
| Sysmiss | 371 |