| Value | Category | Cases | |
|---|---|---|---|
| 1981 | 2 |
5.3%
|
|
| 1982 | 3 |
7.9%
|
|
| 1983 | 4 |
10.5%
|
|
| 1984 | 8 |
21.1%
|
|
| 1985 | 4 |
10.5%
|
|
| 1986 | 6 |
15.8%
|
|
| 1987 | 7 |
18.4%
|
|
| 1988 | 4 |
10.5%
|
|
| Sysmiss | 61 |