| Value | Category | Cases | |
|---|---|---|---|
| 1982 | 2 |
0.4%
|
|
| 1991 | 21 |
4.1%
|
|
| 1992 | 95 |
18.4%
|
|
| 1993 | 159 |
30.9%
|
|
| 1994 | 58 |
11.3%
|
|
| 7777 | 178 |
34.6%
|
|
| 9999 | 2 |
0.4%
|
|
| Sysmiss | 9114 |