| Year | Count |
|---|---|
| 1960 | 9 |
| 1961 | 15 |
| 1963 | 51 |
| 1964 | 27 |
| 1965 | 28 |
| 1966 | 36 |
| 1967 | 44 |
| 1968 | 110 |
| 1969 | 137 |
| 1970 | 337 |
| 1971 | 321 |
| 1972 | 372 |
| 1973 | 488 |
| 1974 | 479 |
| 1975 | 608 |
| 1976 | 614 |
| 1977 | 556 |
| 1978 | 566 |
| 1979 | 513 |
| 1980 | 483 |
| 1981 | 422 |
| 1982 | 316 |
| 1983 | 289 |
| 1984 | 205 |
| 1985 | 285 |
| 1986 | 192 |
| 1987 | 139 |
| 1988 | 132 |
| 1989 | 69 |
| 1990 | 48 |
| 1991 | 49 |
| 1992 | 47 |
| 1993 | 5 |
| 1997 | 12 |
| 1998 | 24 |