| Value | Category | Cases | |
|---|---|---|---|
| 1996 | 35 |
3.1%
|
|
| 1997 | 115 |
10.2%
|
|
| 1998 | 180 |
16%
|
|
| 1999 | 352 |
31.2%
|
|
| 2000 | 445 |
39.5%
|
|
| 9997 | inconsistent | 1 |
0.1%
|
| 9998 | dk | 0 |
0%
|
| Sysmiss | 5627 |