| Year | Count |
|---|---|
| 1971 | 5 |
| 1972 | 13 |
| 1973 | 15 |
| 1974 | 31 |
| 1975 | 27 |
| 1976 | 42 |
| 1977 | 73 |
| 1978 | 83 |
| 1979 | 56 |
| 1980 | 48 |
| 1981 | 76 |
| 1982 | 93 |
| 1983 | 89 |
| 1984 | 76 |
| 1985 | 104 |
| 1986 | 152 |
| 1987 | 109 |
| 1988 | 163 |
| 1989 | 15 |
| 1989 | 160 |
| 1990 | 180 |
| 1991 | 196 |
| 1992 | 5 |
| 1992 | 295 |
| 1993 | 262 |
| 1994 | 228 |
| 1995 | 277 |
| 1996 | 200 |
| 1997 | 208 |
| 1998 | 261 |
| 1999 | 172 |
| 2000 | 211 |
| 2001 | 210 |
| 2002 | 130 |
| 2003 | 122 |
| 2004 | 139 |
| 2005 | 150 |
| 2006 | 187 |
| 2007 | 107 |
| 2008 | 137 |
| 2009 | 84 |
| 2010 | 124 |
| 2011 | 58 |
| 2012 | 80 |
| 2013 | 44 |
| 2014 | 44 |
| 2015 | 51 |
| 2016 | 26 |
| 2017 | 39 |
| 2018 | 48 |
| 2019 | 16 |
| 2020 | 10 |
| 2021 | 10 |
| 2022 | 29 |