Year Measure 1971 815.1192 1972 967.01102 1973 1001.16947 1974 1046.02825 1975 695.84961 1976 736.22259 1977 756.53509 1978 756.53096 1979 685.05034 1980 661.10506 1981 645.7094 1982 768.56764 1983 740.65408 1984 592.91097 1985 579.82467 1986 606.33775 1987 641.79106 1988 612.90126 1989 578.55565 1990 866.25015 1991 712.03823 1992 1444.00701 1993 1523.23506 1994 1693.95822 1995 2048.12725 1996 2101.87928 1997 2156.69622 1998 2235.6107 1999 2261.96088 2000 2274.48601 2001 2275.67238 2002 2343.21148 2003 2405.88886 2004 2376.88899 2005 2392.99909 2006 2366.78973 2007 1921.83874 2008 1156.93866 2009 1218.58063 2010 1213.25709 2011 1203.3958 2012 1038.01771 2013 1015.49649 2014 1055.52347