Year Measure 1960 1873.29247 1961 2187.62364 1962 2389.20988 1963 2479.15851 1964 2715.37501 1965 2938.38464 1966 3197.86486 1967 3345.38785 1968 3628.68529 1969 4071.5561 1970 4570.9068 1971 4889.50427 1972 5516.14053 1973 6046.83031 1974 6140.18668 1975 5946.37733 1976 6545.7468 1977 6726.66369 1978 7330.41447 1979 7930.63137 1980 8295.7861 1981 8493.60537 1982 8533.16174 1983 9124.16463 1984 9808.46626 1985 10482.83161 1986 10622.88818 1987 11358.39475 1988 11778.27227 1989 12034.75727 1990 12485.68365 1991 12470.73043 1992 12514.10157 1993 13012.66943 1994 13603.27636 1995 13591.39667 1996 13721.92376 1997 14454.93873 1998 14846.42082 1999 15075.86719 2000 15305.40981 2001 15709.88325 2002 16140.06697 2003 16445.57256 2004 16777.56585 2005 16117.89033 2006 17215.03729 2007 17160.86312 2008 16349.23333 2009 15243.11039 2010 16484.09428 2011 15710.97376 2012 15689.22331 2013 15510.8355 2014 15249.98938