| Value | Category | Cases | |
|---|---|---|---|
| 1996 | 217 |
10.9%
|
|
| 1997 | 299 |
15%
|
|
| 1998 | 383 |
19.2%
|
|
| 1999 | 538 |
27%
|
|
| 2000 | 552 |
27.7%
|
|
| 9997 | inconsistent | 2 |
0.1%
|
| 9998 | dk | 0 |
0%
|
| Sysmiss | 1998 |