| Year | Count |
|---|---|
| 1973 | 9 |
| 1975 | 10 |
| 1975 | 5 |
| 1976 | 13 |
| 1977 | 15 |
| 1978 | 16 |
| 1979 | 8 |
| 1980 | 16 |
| 1981 | 13 |
| 1982 | 26 |
| 1983 | 17 |
| 1984 | 25 |
| 1985 | 21 |
| 1986 | 19 |
| 1987 | 24 |
| 1988 | 27 |
| 1989 | 39 |
| 1990 | 117 |
| 1991 | 175 |
| 1992 | 155 |
| 1993 | 150 |
| 1994 | 117 |
| 1995 | 72 |
| 1996 | 49 |
| 1997 | 37 |
| 1998 | 21 |
| 1999 | 50 |
| 2000 | 14 |
| 2001 | 33 |
| 2002 | 27 |
| 2004 | 8 |
| 2005 | 10 |
| 2006 | 14 |
| 2007 | 11 |
| 2009 | 5 |
| 2011 | 6 |
| 2012 | 5 |
| 2013 | 5 |
| 2014 | 7 |