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