| Year | Count |
|---|---|
| 1961 | 5 |
| 1963 | 6 |
| 1964 | 9 |
| 1965 | 12 |
| 1966 | 18 |
| 1967 | 21 |
| 1968 | 25 |
| 1969 | 42 |
| 1970 | 51 |
| 1971 | 66 |
| 1972 | 47 |
| 1973 | 62 |
| 1974 | 75 |
| 1975 | 75 |
| 1976 | 58 |
| 1977 | 90 |
| 1978 | 98 |
| 1979 | 64 |
| 1980 | 64 |
| 1981 | 28 |
| 1982 | 31 |
| 1983 | 17 |
| 1984 | 14 |
| 1985 | 15 |
| 1986 | 17 |
| 1987 | 10 |
| 1988 | 16 |
| 1989 | 13 |
| 1990 | 11 |
| 1991 | 5 |
| 1992 | 5 |
| 1993 | 6 |