Year Measure 1971 259.36283 1972 259.90946 1973 305.2643 1974 323.71829 1975 365.26745 1976 412.40725 1977 485.19715 1978 578.81216 1979 726.59119 1980 792.0397 1981 734.27335 1982 899.0665 1983 1037.11175 1984 1215.74422 1985 1279.11497 1986 1328.59574 1987 1309.50306 1988 1336.19132 1989 1329.79738 1990 1305.16878 1991 1092.92267 1992 1306.52052 1993 1321.90773 1994 1369.98891 1995 1415.60036 1996 1372.30868 1997 1355.69322 1998 1314.09065 1999 1274.57825 2000 1237.4067 2001 1238.47248 2002 1264.55038 2003 1040.7909 2004 1202.13056 2005 833.85089 2006 972.99753 2007 768.85055 2008 750.18677 2009 836.50413 2010 1195.99381 2011 1272.73088 2012 1110.27478 2013 1397.12533 2014 1305.68747