Year Measure 1960 3082.71156 1961 2916.70623 1962 3028.29837 1963 3279.60227 1964 3306.81596 1965 3444.55135 1966 3639.77093 1967 3594.36179 1968 3924.13444 1969 3553.47669 1970 4231.9921 1971 4378.31032 1972 4403.96965 1973 5268.96574 1974 5132.19707 1975 5071.63534 1976 5085.581 1977 5602.87017 1978 5710.71008 1979 6515.05969 1980 6560.99817 1981 7178.86936 1982 7076.20799 1983 7254.28628 1984 7531.26996 1985 7334.90193 1986 7605.56378 1987 7857.45488 1988 7882.47377 1989 7983.03751 1990 8907.79198 1991 8054.35672 1992 7755.39442 1993 8249.53645 1994 8293.41293 1995 8255.76891 1996 8847.78518 1997 8584.1005 1998 9036.6543 1999 10038.31192 2000 11091.54887 2001 10589.46619 2002 10804.64172 2003 10731.32864 2004 10524.2507 2005 10524.8775 2006 12734.00662 2007 14746.03134 2008 16353.83127 2009 16911.07978 2010 17023.16682 2011 18157.5981 2012 17630.07147 2013 18178.13901 2014 17916.12042 2015 17478.89304