Year Measure 1971 547.17836 1972 541.01768 1973 523.57372 1974 577.94704 1975 593.46571 1976 628.55708 1977 617.94821 1978 774.49162 1979 884.62394 1980 861.98386 1981 896.53399 1982 887.86123 1983 1010.41784 1984 1016.39305 1985 996.74529 1986 1087.91791 1987 1068.50569 1988 1087.70215 1989 1159.35468 1990 1210.3968 1991 1453.77975 1992 1562.13071 1993 1647.42146 1994 1598.62438 1995 1686.69339 1996 1819.56171 1997 2064.46854 1998 1913.80233 1999 1892.21927 2000 2108.60056 2001 2146.88884 2002 2173.29637 2003 2282.2512 2004 2407.06295 2005 2561.60837 2006 2527.96485 2007 2718.08406 2008 2790.46404 2009 2603.93297 2010 2610.30953 2011 2672.12816 2012 2669.14059 2013 2955.79156 2014 2967.5413