| Year | Count |
|---|---|
| 1960 | 10 |
| 1963 | 10 |
| 1964 | 7 |
| 1965 | 8 |
| 1966 | 10 |
| 1967 | 6 |
| 1968 | 11 |
| 1969 | 13 |
| 1970 | 13 |
| 1971 | 10 |
| 1972 | 6 |
| 1973 | 8 |
| 1974 | 11 |
| 1977 | 24 |
| 1978 | 22 |
| 1979 | 26 |
| 1980 | 26 |
| 1981 | 18 |
| 1982 | 15 |
| 1983 | 15 |
| 1984 | 16 |
| 1985 | 14 |
| 1986 | 15 |
| 1987 | 17 |
| 1988 | 24 |
| 1989 | 15 |
| 1990 | 15 |
| 1991 | 12 |
| 1992 | 12 |
| 1993 | 16 |
| 1994 | 11 |
| 1995 | 8 |
| 1996 | 7 |
| 1997 | 6 |
| 1998 | 6 |