| Year | Count |
|---|---|
| 1978 | 5 |
| 1981 | 8 |
| 1982 | 5 |
| 1983 | 9 |
| 1984 | 18 |
| 1985 | 22 |
| 1986 | 22 |
| 1987 | 37 |
| 1988 | 49 |
| 1989 | 69 |
| 1990 | 94 |
| 1991 | 134 |
| 1992 | 104 |
| 1993 | 106 |
| 1994 | 129 |
| 1995 | 82 |
| 1996 | 86 |
| 1997 | 64 |
| 1998 | 43 |
| 1999 | 42 |
| 2000 | 30 |
| 2001 | 30 |
| 2002 | 17 |
| 2003 | 25 |
| 2004 | 12 |
| 2005 | 7 |
| 2006 | 9 |
| 2007 | 15 |
| 2008 | 10 |
| 2009 | 12 |
| 2010 | 14 |
| 2011 | 5 |
| 2012 | 6 |
| 2013 | 12 |
| 2014 | 8 |
| 2015 | 10 |
| 2016 | 14 |
| 2017 | 18 |
| 2018 | 10 |
| 2019 | 5 |
| 2020 | 5 |
| 2021 | 7 |