| Year | Count |
|---|---|
| 1973 | 6 |
| 1976 | 15 |
| 1977 | 12 |
| 1978 | 10 |
| 1979 | 11 |
| 1980 | 7 |
| 1981 | 6 |
| 1982 | 19 |
| 1983 | 7 |
| 1984 | 24 |
| 1985 | 29 |
| 1986 | 18 |
| 1987 | 55 |
| 1988 | 24 |
| 1989 | 40 |
| 1990 | 37 |
| 1991 | 55 |
| 1992 | 86 |
| 1993 | 119 |
| 1994 | 107 |
| 1995 | 73 |
| 1996 | 133 |
| 1997 | 145 |
| 1998 | 131 |
| 1999 | 101 |
| 2000 | 136 |
| 2001 | 151 |
| 2002 | 175 |
| 2003 | 253 |
| 2004 | 437 |
| 2005 | 468 |
| 2006 | 557 |
| 2007 | 510 |
| 2008 | 439 |
| 2009 | 292 |
| 2010 | 240 |
| 2011 | 248 |
| 2012 | 172 |
| 2013 | 71 |
| 2014 | 117 |
| 2015 | 109 |
| 2016 | 150 |
| 2017 | 97 |
| 2018 | 95 |
| 2019 | 57 |
| 2020 | 50 |
| 2021 | 58 |
| 2022 | 90 |
| 2023 | 42 |
| 2024 | 45 |