| Year | Count |
|---|---|
| 1967 | 10 |
| 1968 | 26 |
| 1969 | 10 |
| 1971 | 30 |
| 1972 | 19 |
| 1973 | 5 |
| 1974 | 11 |
| 1975 | 12 |
| 1976 | 22 |
| 1977 | 15 |
| 1978 | 26 |
| 1979 | 12 |
| 1980 | 15 |
| 1981 | 25 |
| 1982 | 27 |
| 1983 | 13 |
| 1984 | 25 |
| 1985 | 22 |
| 1986 | 9 |
| 1987 | 16 |
| 1988 | 10 |
| 1988 | 19 |
| 1989 | 25 |
| 1990 | 15 |
| 1991 | 13 |
| 1992 | 12 |
| 1993 | 18 |
| 1994 | 27 |
| 1995 | 61 |
| 1996 | 27 |
| 1997 | 52 |
| 1998 | 47 |
| 1999 | 40 |
| 2000 | 57 |
| 2001 | 85 |
| 2002 | 42 |
| 2003 | 68 |
| 2004 | 74 |
| 2005 | 127 |
| 2006 | 150 |
| 2007 | 69 |
| 2008 | 120 |
| 2009 | 94 |
| 2010 | 65 |
| 2011 | 64 |
| 2012 | 41 |
| 2013 | 37 |
| 2014 | 29 |
| 2015 | 33 |
| 2016 | 32 |
| 2017 | 28 |
| 2018 | 7 |
| 2019 | 9 |
| 2021 | 25 |
| 2022 | 6 |
| 2023 | 11 |