- 1970 - 62.90
- 1971 - 64.40
- 1972 - 61.40
- 1973 - 65.40
- 1974 - 72.80
- 1975 - 75.70
- 1976 - 75.70
- 1977 - 34.90*
- 1978 - 38.50
- 1979 - 42.10
- 1980 - 44.95
- 1981 - 47.64
- 1982 - 49.82
- 1983 - 51.56
| - 1984 - 51.56
- 1985 - 51.56
- 1986 - 51.56
- 1987 - 19.15
- 1988 - 19.95*
- 1989 - 22.89
- 1990 - 24.89
- 1991 - 25.63
- 1992 - 26.23
- 1993 - 26.50
- 1994 - 26.50
- 1995 - 26.50
- 1996 - 26.50
- 1997 - 26.50
| - 1998 - 28.90*
- 1999 - 29.55
- 2000 - 30.50
- 2001 - 32.25
- 2002 - 30.93*
- 2003 - 32.83
- 2004 - 33.33
- 2005 - 34.21
- 2006 - 34.71
- 2007 - 25.99*
- 2008 - 25.99
- 2009 - 27.24
- 2010 - 27.24
- 2011 - 28.75
|