| Year | Count |
|---|---|
| 1961 | 8 |
| 1963 | 7 |
| 1964 | 8 |
| 1972 | 6 |
| 1979 | 5 |
| 1980 | 8 |
| 1981 | 8 |
| 1982 | 10 |
| 1983 | 9 |
| 1984 | 8 |
| 1985 | 13 |
| 1986 | 10 |
| 1987 | 15 |
| 1988 | 17 |
| 1989 | 20 |
| 1990 | 27 |
| 1991 | 39 |
| 1992 | 30 |
| 1993 | 22 |
| 1994 | 36 |
| 1995 | 51 |
| 1996 | 47 |
| 1997 | 64 |
| 1998 | 39 |
| 1999 | 44 |
| 2000 | 35 |
| 2001 | 25 |
| 2002 | 22 |
| 2003 | 22 |
| 2004 | 37 |
| 2005 | 27 |
| 2006 | 30 |
| 2007 | 14 |
| 2008 | 12 |
| 2009 | 14 |
| 2010 | 16 |
| 2011 | 9 |
| 2012 | 15 |
| 2013 | 9 |
| 2014 | 9 |
| 2015 | 14 |
| 2016 | 20 |
| 2017 | 12 |
| 2018 | 12 |
| 2020 | 8 |
| 2021 | 8 |
| 2024 | 6 |