| Year | Count |
|---|---|
| 1973 | 6 |
| 1978 | 5 |
| 1980 | 11 |
| 1981 | 18 |
| 1982 | 32 |
| 1983 | 51 |
| 1984 | 47 |
| 1985 | 147 |
| 1986 | 142 |
| 1987 | 165 |
| 1988 | 263 |
| 1989 | 194 |
| 1990 | 195 |
| 1991 | 239 |
| 1992 | 177 |
| 1993 | 132 |
| 1994 | 96 |
| 1995 | 64 |
| 1996 | 83 |
| 1997 | 76 |
| 1998 | 75 |
| 1999 | 23 |
| 2000 | 29 |
| 2002 | 10 |
| 2003 | 12 |
| 2004 | 12 |
| 2005 | 22 |
| 2006 | 8 |
| 2007 | 5 |
| 2009 | 12 |
| 2013 | 5 |
| 2017 | 5 |