Year Measure 1971 666.07486 1972 648.808 1973 658.31892 1974 678.35218 1975 679.91458 1976 672.42446 1977 678.50924 1978 641.41797 1979 622.80873 1980 648.52101 1981 636.64554 1982 632.72538 1983 568.24488 1984 568.78988 1985 541.32043 1986 538.88826 1987 540.97437 1988 520.40017 1989 469.98569 1990 445.98055 1991 428.52211 1992 408.43313 1993 427.60889 1994 434.80119 1995 456.3958 1996 462.3251 1997 440.55803 1998 456.55964 1999 479.5173 2000 471.60814 2001 449.14127 2002 446.34076 2003 432.02785 2004 472.06627 2005 494.18763 2006 474.01111 2007 506.67157 2008 524.93249 2009 543.48431 2010 635.49159 2011 638.44247 2012 677.96907 2013 666.43278 2014 767.68951