Year Measure 1971 415.90598 1972 406.50677 1973 439.95459 1974 428.83247 1975 442.13067 1976 450.65062 1977 456.75778 1978 451.7899 1979 465.56602 1980 472.91474 1981 462.54288 1982 461.90769 1983 488.85484 1984 427.82996 1985 437.42964 1986 425.77979 1987 433.35542 1988 446.42096 1989 457.39406 1990 463.44304 1991 451.40009 1992 460.57014 1993 449.35187 1994 470.33558 1995 481.44149 1996 486.67431 1997 500.83783 1998 504.00575 1999 506.23132 2000 512.74833 2001 480.65042 2002 477.11867 2003 468.65996 2004 458.07829 2005 450.35009 2006 439.23964 2007 432.80676 2008 441.91993 2009 414.07766 2010 431.01025 2011 426.82199 2012 446.53887 2013 454.85666 2014 476.24472