| Year | Count |
|---|---|
| 1970 | 7 |
| 1971 | 7 |
| 1972 | 6 |
| 1973 | 5 |
| 1974 | 13 |
| 1975 | 15 |
| 1976 | 14 |
| 1977 | 28 |
| 1978 | 37 |
| 1979 | 18 |
| 1981 | 8 |
| 1982 | 8 |
| 1983 | 9 |
| 1984 | 8 |
| 1985 | 12 |
| 1987 | 10 |
| 1989 | 10 |
| 1991 | 10 |
| 1994 | 6 |
| 1996 | 10 |
| 1997 | 5 |
| 1998 | 7 |
| 1999 | 9 |
| 2000 | 11 |
| 2001 | 8 |
| 2002 | 7 |
| 2003 | 6 |
| 2004 | 19 |
| 2005 | 317 |
| 2006 | 286 |
| 2007 | 306 |
| 2008 | 312 |
| 2009 | 188 |
| 2010 | 158 |
| 2011 | 188 |
| 2012 | 107 |
| 2013 | 109 |
| 2014 | 133 |
| 2015 | 147 |
| 2016 | 137 |
| 2017 | 157 |
| 2018 | 92 |
| 2019 | 82 |
| 2020 | 96 |
| 2021 | 76 |
| 2022 | 40 |
| 2023 | 73 |
| 2024 | 45 |