| Year | Count |
|---|---|
| 1966 | 10 |
| 1967 | 5 |
| 1968 | 7 |
| 1969 | 12 |
| 1970 | 25 |
| 1971 | 24 |
| 1972 | 27 |
| 1973 | 54 |
| 1974 | 24 |
| 1975 | 82 |
| 1976 | 79 |
| 1977 | 101 |
| 1978 | 89 |
| 1979 | 202 |
| 1980 | 223 |
| 1981 | 184 |
| 1982 | 182 |
| 1983 | 252 |
| 1984 | 277 |
| 1985 | 240 |
| 1986 | 262 |
| 1987 | 274 |
| 1988 | 293 |
| 1989 | 317 |
| 1989 | 5 |
| 1990 | 294 |
| 1991 | 398 |
| 1992 | 248 |
| 1993 | 234 |
| 1994 | 286 |
| 1995 | 167 |
| 1996 | 189 |
| 1997 | 153 |
| 1998 | 133 |
| 1999 | 75 |
| 2000 | 76 |
| 2001 | 49 |
| 2002 | 34 |
| 2003 | 42 |
| 2004 | 42 |
| 2005 | 34 |
| 2006 | 40 |
| 2007 | 32 |
| 2008 | 54 |
| 2009 | 14 |
| 2010 | 5 |
| 2012 | 6 |
| 2013 | 10 |
| 2015 | 42 |
| 2016 | 33 |
| 2017 | 21 |
| 2018 | 12 |