| Year | Count |
|---|---|
| 1980 | 10 |
| 1981 | 6 |
| 1982 | 19 |
| 1983 | 5 |
| 1984 | 5 |
| 1985 | 5 |
| 1986 | 12 |
| 1987 | 16 |
| 1988 | 44 |
| 1989 | 35 |
| 1990 | 18 |
| 1991 | 57 |
| 1992 | 77 |
| 1993 | 58 |
| 1994 | 101 |
| 1995 | 81 |
| 1996 | 122 |
| 1997 | 110 |
| 1998 | 202 |
| 1999 | 125 |
| 2000 | 141 |
| 2001 | 149 |
| 2002 | 143 |
| 2003 | 109 |
| 2004 | 127 |
| 2005 | 93 |
| 2006 | 54 |
| 2007 | 93 |
| 2008 | 46 |
| 2009 | 82 |
| 2010 | 39 |
| 2011 | 31 |
| 2012 | 25 |
| 2013 | 7 |
| 2014 | 6 |
| 2015 | 10 |
| 2017 | 5 |
| 2019 | 6 |