Year Measure 1971 505.40129 1972 573.37287 1973 586.31507 1974 600.94496 1975 598.22211 1976 602.92331 1977 601.95201 1978 602.62646 1979 611.58214 1980 591.23756 1981 597.86903 1982 596.93329 1983 620.7953 1984 639.76461 1985 521.88737 1986 530.47909 1987 588.6271 1988 552.19028 1989 533.76681 1990 558.88464 1991 552.429 1992 600.9005 1993 571.46949 1994 644.41487 1995 664.86502 1996 682.13749 1997 748.65425 1998 778.52869 1999 797.02109 2000 843.16276 2001 805.08113 2002 841.27143 2003 784.21445 2004 698.73145 2005 748.54675 2006 763.91664 2007 766.07435 2008 757.67933 2009 733.5581 2010 760.7702 2011 764.80097 2012 797.40156 2013 742.47206 2014 734.4079