| Year | Count |
|---|---|
| 1960 | 7 |
| 1961 | 14 |
| 1965 | 14 |
| 1966 | 10 |
| 1967 | 10 |
| 1968 | 20 |
| 1969 | 32 |
| 1970 | 49 |
| 1971 | 78 |
| 1972 | 113 |
| 1973 | 91 |
| 1974 | 145 |
| 1975 | 152 |
| 1976 | 118 |
| 1977 | 169 |
| 1978 | 128 |
| 1979 | 208 |
| 1980 | 173 |
| 1981 | 156 |
| 1982 | 122 |
| 1983 | 157 |
| 1984 | 130 |
| 1985 | 129 |
| 1986 | 126 |
| 1987 | 131 |
| 1988 | 103 |
| 1989 | 113 |
| 1990 | 108 |
| 1991 | 65 |
| 1992 | 110 |
| 1993 | 41 |
| 1994 | 49 |
| 1995 | 37 |
| 1996 | 19 |
| 1997 | 15 |
| 1998 | 37 |
| 1999 | 42 |
| 2000 | 22 |
| 2001 | 41 |
| 2002 | 21 |
| 2003 | 12 |
| 2004 | 33 |
| 2005 | 5 |
| 2006 | 38 |
| 2007 | 45 |
| 2008 | 10 |
| 2009 | 36 |
| 2010 | 18 |
| 2011 | 15 |
| 2013 | 16 |
| 2016 | 15 |