| Value | Category | Cases | |
|---|---|---|---|
| 1996 | 100 |
6.2%
|
|
| 1997 | 169 |
10.5%
|
|
| 1998 | 290 |
18%
|
|
| 1999 | 511 |
31.8%
|
|
| 2000 | 537 |
33.4%
|
|
| 9997 | inconsistent | 1 |
0.1%
|
| 9998 | dk | 0 |
0%
|
| Sysmiss | 5147 |