| Value | Category | Cases | |
|---|---|---|---|
| 1960 | 116 |
14.4%
|
|
| 1965 | 115 |
14.3%
|
|
| 1970 | 115 |
14.3%
|
|
| 1975 | 116 |
14.4%
|
|
| 1980 | 115 |
14.3%
|
|
| 1985 | 114 |
14.2%
|
|
| 1990 | 114 |
14.2%
|