1966 284.20 1967 277.00 1968 282.20 1969 276.80 1970 276.80 1971 275.40 1972 275.30 1973 269.50 1974 269.50 1975 269.50 1976 269.50 1977 263.80 1978 266.90 1979 262.09 1980 261.68 1981 260.89 1982 257.44 1983 261.65 1984 255.80 1985 256.71 1986 258.25 1987 264.05 1988 261.25 1989 255.61 1990 258.13 1991 257.00 1992 261.30 1993 261.69 1994 257.25 1995 264.13 1996 252.56 1997 264.53 1998 259.30 1999 263.44 2000 272.87 2001 270.30 2002 265.27 2003 264.40 2004 261.57