| Year | Count |
|---|---|
| 1971 | 5 |
| 1972 | 11 |
| 1973 | 21 |
| 1974 | 17 |
| 1975 | 23 |
| 1976 | 12 |
| 1977 | 15 |
| 1978 | 35 |
| 1979 | 47 |
| 1980 | 30 |
| 1981 | 28 |
| 1982 | 58 |
| 1983 | 47 |
| 1984 | 66 |
| 1985 | 71 |
| 1986 | 67 |
| 1987 | 71 |
| 1988 | 102 |
| 1989 | 151 |
| 1990 | 163 |
| 1991 | 188 |
| 1992 | 227 |
| 1993 | 108 |
| 1994 | 94 |
| 1995 | 88 |
| 1996 | 90 |
| 1997 | 56 |
| 1998 | 104 |
| 1999 | 89 |
| 2000 | 94 |
| 2001 | 66 |
| 2002 | 64 |
| 2003 | 68 |
| 2004 | 75 |
| 2005 | 109 |
| 2006 | 70 |
| 2007 | 59 |
| 2008 | 64 |
| 2009 | 49 |
| 2010 | 72 |
| 2011 | 74 |
| 2012 | 62 |
| 2013 | 44 |
| 2014 | 43 |
| 2015 | 28 |
| 2016 | 27 |
| 2017 | 37 |
| 2018 | 18 |
| 2019 | 11 |
| 2021 | 12 |
| 2022 | 15 |
| 2024 | 6 |