| Value | Category | Cases | |
|---|---|---|---|
| 1995 | 4 |
0.2%
|
|
| 1996 | 121 |
7%
|
|
| 1997 | 167 |
9.7%
|
|
| 1998 | 307 |
17.9%
|
|
| 1999 | 555 |
32.3%
|
|
| 2000 | 563 |
32.8%
|
|
| 9997 | inconsistent | 1 |
0.1%
|
| 9998 | dk | 0 |
0%
|
| Sysmiss | 5037 |