| Year | Count |
|---|---|
| 1981 | 6 |
| 1982 | 5 |
| 1983 | 5 |
| 1984 | 12 |
| 1985 | 57 |
| 1986 | 80 |
| 1987 | 65 |
| 1988 | 60 |
| 1989 | 102 |
| 1990 | 103 |
| 1991 | 150 |
| 1992 | 229 |
| 1993 | 176 |
| 1994 | 169 |
| 1995 | 148 |
| 1996 | 108 |
| 1997 | 104 |
| 1998 | 136 |
| 1999 | 115 |
| 2000 | 103 |
| 2001 | 88 |
| 2002 | 53 |
| 2003 | 74 |
| 2004 | 20 |
| 2005 | 61 |
| 2006 | 70 |
| 2007 | 49 |
| 2008 | 49 |
| 2009 | 29 |
| 2010 | 31 |
| 2011 | 31 |
| 2012 | 20 |
| 2013 | 10 |
| 2014 | 25 |
| 2015 | 12 |