| Year | Count |
|---|---|
| 1971 | 7 |
| 1972 | 13 |
| 1973 | 11 |
| 1974 | 16 |
| 1975 | 27 |
| 1976 | 12 |
| 1977 | 56 |
| 1978 | 65 |
| 1979 | 85 |
| 1980 | 100 |
| 1981 | 42 |
| 1982 | 48 |
| 1983 | 55 |
| 1984 | 35 |
| 1985 | 104 |
| 1986 | 87 |
| 1987 | 163 |
| 1988 | 173 |
| 1989 | 121 |
| 1990 | 145 |
| 1991 | 228 |
| 1992 | 212 |
| 1993 | 158 |
| 1994 | 175 |
| 1995 | 101 |
| 1996 | 124 |
| 1997 | 126 |
| 1998 | 130 |
| 1999 | 89 |
| 2000 | 81 |
| 2001 | 114 |
| 2002 | 56 |
| 2003 | 58 |
| 2004 | 125 |
| 2005 | 134 |
| 2006 | 84 |
| 2007 | 81 |
| 2008 | 72 |
| 2009 | 50 |
| 2010 | 48 |
| 2011 | 26 |
| 2012 | 39 |
| 2013 | 13 |
| 2014 | 36 |
| 2015 | 5 |
| 2016 | 31 |
| 2017 | 12 |
| 2018 | 29 |
| 2020 | 37 |
| 2021 | 5 |
| 2022 | 16 |
| 2023 | 10 |