| Year | Count |
|---|---|
| 1971 | 5 |
| 1974 | 6 |
| 1976 | 7 |
| 1983 | 5 |
| 1984 | 5 |
| 1985 | 11 |
| 1986 | 6 |
| 1987 | 18 |
| 1988 | 11 |
| 1989 | 13 |
| 1990 | 18 |
| 1991 | 17 |
| 1992 | 25 |
| 1993 | 22 |
| 1994 | 23 |
| 1995 | 18 |
| 1996 | 41 |
| 1997 | 144 |
| 1998 | 306 |
| 1999 | 350 |
| 2000 | 414 |
| 2001 | 460 |
| 2002 | 384 |
| 2003 | 325 |
| 2004 | 152 |
| 2005 | 140 |
| 2006 | 110 |
| 2007 | 129 |
| 2008 | 189 |
| 2009 | 86 |
| 2010 | 99 |
| 2011 | 90 |
| 2012 | 51 |
| 2013 | 102 |
| 2014 | 41 |
| 2015 | 72 |
| 2016 | 68 |
| 2017 | 60 |
| 2018 | 48 |
| 2019 | 28 |
| 2020 | 74 |
| 2021 | 18 |
| 2022 | 37 |
| 2023 | 11 |
| 2024 | 40 |