| Year | Count |
|---|---|
| 1968 | 6 |
| 1969 | 5 |
| 1970 | 15 |
| 1971 | 42 |
| 1972 | 47 |
| 1973 | 61 |
| 1974 | 86 |
| 1975 | 167 |
| 1976 | 166 |
| 1977 | 204 |
| 1978 | 206 |
| 1979 | 261 |
| 1980 | 273 |
| 1981 | 307 |
| 1982 | 269 |
| 1983 | 272 |
| 1984 | 183 |
| 1985 | 212 |
| 1986 | 169 |
| 1987 | 147 |
| 1988 | 145 |
| 1989 | 90 |
| 1990 | 100 |
| 1991 | 87 |
| 1992 | 100 |
| 1993 | 107 |
| 1994 | 63 |
| 1995 | 34 |
| 1996 | 69 |
| 1997 | 113 |
| 1998 | 89 |
| 1999 | 86 |
| 2000 | 54 |
| 2002 | 6 |
| 2007 | 5 |
| 2010 | 10 |