Year Measure 1960 4548.20524 1961 4630.02414 1962 5094.31021 1963 7016.35298 1964 8692.60107 1965 9107.08899 1966 9541.92186 1967 9495.66411 1968 9209.46851 1969 10260.74074 1970 10649.49539 1971 11871.35135 1972 11661.85805 1973 11796.26195 1974 13108.01296 1975 10642.15072 1976 11487.78453 1977 10443.93648 1978 10806.42087 1979 10982.31805 1980 10784.01758 1981 11089.05469 1982 10992.40818 1983 11137.1854 1984 11737.76906 1985 12064.16039 1986 12159.46573 1987 12275.118 1988 13423.48373 1989 13537.5232 1990 13667.67055 1991 14087.8553 1992 12927.90208 1993 12632.24102 1994 13665.07415 1995 14920.77088 1996 14629.73022 1997 15134.10418 1998 15460.32494 1999 14990.41756 2000 15668.11827 2001 15616.32977 2002 15980.2768 2003 16258.88449 2004 16300.11242 2005 15644.14672 2006 16456.60412 2007 16352.3218 2008 15937.78778 2009 14425.96473 2010 16829.96254 2011 15586.08423 2012 14703.94353 2013 14193.16843 2014 13914.67845