Year Measure 1971 893.15323 1972 890.73493 1973 841.94113 1974 821.9737 1975 731.37216 1976 762.28919 1977 777.93721 1978 793.56355 1979 826.67181 1980 841.30941 1981 841.76333 1982 760.1328 1983 773.83892 1984 801.36718 1985 786.68828 1986 808.50135 1987 820.57551 1988 913.24609 1989 1006.65103 1990 1057.93803 1991 1064.48601 1992 1133.11635 1993 1143.58753 1994 1211.33062 1995 1282.9445 1996 1401.31465 1997 1548.09639 1998 1582.22522 1999 1660.00993 2000 1648.96551 2001 1599.05747 2002 1636.46623 2003 1635.06923 2004 1722.28949 2005 1756.5981 2006 1809.0608 2007 1856.83084 2008 1820.25367 2009 1754.22334 2010 1815.2759 2011 1959.3588 2012 2149.49145 2013 2215.80043 2014 2049.68883 2015 2028.88601