Year Measure 1971 272.52277 1972 286.852 1973 315.93842 1974 323.83346 1975 365.18272 1976 456.7441 1977 455.17351 1978 543.70324 1979 542.47746 1980 641.12656 1981 770.30164 1982 842.44749 1983 877.7647 1984 926.23546 1985 903.80682 1986 932.42121 1987 951.89386 1988 907.19046 1989 875.39643 1990 919.50164 1991 901.57144 1992 958.0336 1993 898.89415 1994 918.4368 1995 940.65303 1996 935.76123 1997 933.04861 1998 946.11166 1999 926.80451 2000 953.46993 2001 927.5461 2002 956.9495 2003 958.59415 2004 1123.2919 2005 1168.39995 2006 1154.9267 2007 1164.01496 2008 1089.23989 2009 1093.36639 2010 988.98333 2011 932.80068 2012 982.14155 2013 918.45677 2014 928.52048