| Value | Category | Cases | |
|---|---|---|---|
| -2 | do not know | 0 |
0%
|
| 1988 | 1 |
0%
|
|
| 1996 | 242 |
11.1%
|
|
| 1997 | 291 |
13.4%
|
|
| 1998 | 366 |
16.8%
|
|
| 1999 | 409 |
18.8%
|
|
| 2000 | 596 |
27.4%
|
|
| 2001 | 270 |
12.4%
|
|
| Sysmiss | 1 |