Year Measure 1971 473.0595 1972 474.61166 1973 482.53166 1974 482.84662 1975 517.92196 1976 540.04053 1977 558.58533 1978 558.19015 1979 577.77853 1980 520.68076 1981 494.01968 1982 473.46423 1983 446.28958 1984 460.09404 1985 457.51851 1986 428.92983 1987 442.70508 1988 449.89248 1989 456.35346 1990 476.1671 1991 478.28755 1992 492.76297 1993 479.76042 1994 493.96012 1995 511.15806 1996 513.63722 1997 525.55992 1998 558.91422 1999 600.2719 2000 604.31579 2001 602.79451 2002 593.54314 2003 602.6144 2004 606.24759 2005 595.59043 2006 591.31315 2007 621.27521 2008 582.39989 2009 654.03325 2010 696.79463 2011 729.14844 2012 725.05353 2013 772.30262 2014 830.09452