| Value | Category | Cases | |
|---|---|---|---|
| 1980 | 12 |
5.1%
|
|
| 1981 | 24 |
10.3%
|
|
| 1982 | 30 |
12.8%
|
|
| 1983 | 19 |
8.1%
|
|
| 1984 | 30 |
12.8%
|
|
| 1985 | 30 |
12.8%
|
|
| 1986 | 26 |
11.1%
|
|
| 1987 | 41 |
17.5%
|
|
| 1988 | 21 |
9%
|
|
| 1989 | 1 |
0.4%
|