| Value | Category | Cases | |
|---|---|---|---|
| 1988 | 1 |
0.2%
|
|
| 1989 | 1 |
0.2%
|
|
| 1996 | 1 |
0.2%
|
|
| 1997 | 27 |
5.3%
|
|
| 1998 | 165 |
32.5%
|
|
| 1999 | 181 |
35.7%
|
|
| 2000 | 131 |
25.8%
|
|
| Sysmiss | 8489 |