| Value | Category | Cases | |
|---|---|---|---|
| 1997 | 3 |
25%
|
|
| 1998 | 4 |
33.3%
|
|
| 1999 | 4 |
33.3%
|
|
| 2000 | 1 |
8.3%
|
|
| 9997 | Missing | 0 |
0%
|
| Sysmiss | 1878 |