| Year | Count |
|---|---|
| 1967 | 6 |
| 1970 | 13 |
| 1972 | 12 |
| 1973 | 26 |
| 1974 | 29 |
| 1975 | 35 |
| 1976 | 23 |
| 1977 | 29 |
| 1978 | 39 |
| 1979 | 25 |
| 1980 | 33 |
| 1981 | 38 |
| 1982 | 16 |
| 1983 | 14 |
| 1984 | 36 |
| 1985 | 25 |
| 1986 | 34 |
| 1987 | 40 |
| 1988 | 109 |
| 1989 | 105 |
| 1990 | 99 |
| 1991 | 141 |
| 1992 | 171 |
| 1993 | 191 |
| 1994 | 241 |
| 1995 | 160 |
| 1996 | 210 |
| 1997 | 159 |
| 1998 | 204 |
| 1999 | 177 |
| 2000 | 185 |
| 2001 | 123 |
| 2002 | 118 |
| 2003 | 123 |
| 2004 | 125 |
| 2005 | 104 |
| 2006 | 112 |
| 2007 | 44 |
| 2008 | 31 |
| 2009 | 86 |
| 2010 | 17 |
| 2011 | 22 |
| 2012 | 20 |
| 2013 | 25 |
| 2014 | 15 |
| 2015 | 10 |
| 2016 | 15 |