| Value | Category | Cases | |
|---|---|---|---|
| 1982 | 1 |
0.5%
|
|
| 1988 | 1 |
0.5%
|
|
| 1989 | 1 |
0.5%
|
|
| 1990 | 1 |
0.5%
|
|
| 1993 | 6 |
3.3%
|
|
| 1994 | 6 |
3.3%
|
|
| 1995 | 9 |
4.9%
|
|
| 1996 | 7 |
3.8%
|
|
| 1997 | 12 |
6.5%
|
|
| 1998 | 15 |
8.2%
|
|
| 1999 | 62 |
33.7%
|
|
| 2000 | 44 |
23.9%
|
|
| 9998 | don't know | 19 |
10.3%
|
| Sysmiss | 621 |