Year Measure 1971 785.31838 1972 789.56816 1973 958.86179 1974 964.36123 1975 840.25019 1976 892.93145 1977 696.19729 1978 830.10329 1979 895.28834 1980 949.41567 1981 901.27983 1982 678.58272 1983 729.91244 1984 740.01282 1985 870.05372 1986 965.15717 1987 996.94668 1988 741.76614 1989 732.69347 1990 722.85736 1991 878.60686 1992 868.42695 1993 1210.11468 1994 1292.97831 1995 1453.58763 1996 1514.07215 1997 1697.79123 1998 1656.88124 1999 1710.08121 2000 1516.69208 2001 1565.7032 2002 1483.73087 2003 1413.62688 2004 1368.52902 2005 1264.72239 2006 1181.61583 2007 1033.92785 2008 1321.00022 2009 1589.32203 2010 1470.65221 2011 1383.15584 2012 1458.60165 2013 1340.26579 2014 1337.36603