| Value | Category | Cases | |
|---|---|---|---|
| 1995 | 12 |
1.9%
|
|
| 1996 | 51 |
8.1%
|
|
| 1997 | 72 |
11.5%
|
|
| 1998 | 90 |
14.3%
|
|
| 1999 | 142 |
22.6%
|
|
| 2000 | 58 |
9.2%
|
|
| 9997 | Missing | 203 |
32.3%
|
| Sysmiss | 2076 |