| Year | Count |
|---|---|
| 1973 | 6 |
| 1974 | 5 |
| 1975 | 9 |
| 1976 | 6 |
| 1977 | 6 |
| 1978 | 26 |
| 1979 | 15 |
| 1980 | 12 |
| 1981 | 41 |
| 1982 | 48 |
| 1983 | 44 |
| 1984 | 43 |
| 1985 | 61 |
| 1986 | 165 |
| 1987 | 245 |
| 1988 | 223 |
| 1989 | 143 |
| 1990 | 108 |
| 1991 | 155 |
| 1992 | 122 |
| 1993 | 66 |
| 1994 | 60 |
| 1995 | 37 |
| 1996 | 41 |
| 1997 | 52 |
| 1998 | 79 |
| 1999 | 8 |
| 2000 | 19 |
| 2002 | 5 |
| 2004 | 32 |
| 2005 | 5 |
| 2006 | 5 |
| 2007 | 5 |