Year Measure 1965 1426.89966 1966 1447.93795 1967 1476.04958 1968 1506.99949 1969 1607.81594 1970 1730.16287 1971 1836.34975 1972 1880.5388 1973 2039.36703 1974 2101.98707 1975 2173.24697 1976 2311.17337 1977 2428.82933 1978 2674.05933 1979 2638.20497 1980 2646.30419 1981 2630.04292 1982 2630.75848 1983 2594.39478 1984 2697.39415 1985 2794.25194 1986 2787.68417 1987 2894.82745 1988 2863.97624 1989 2874.89581 1990 2774.49203 1991 2642.92257 1992 2423.17945 1993 2481.44841 1994 2406.68835 1995 2503.0778 1996 2572.97436 1997 2527.30163 1998 2502.20405 1999 2490.7126 2000 2448.14034 2001 2512.67485 2002 2520.15247 2003 2580.2075 2004 2579.29172 2005 2731.0397 2006 2713.25708 2007 2658.03637 2008 2636.64677 2009 2478.1017 2010 2568.94899 2011 2500.32136 2012 2365.5537 2013 2271.94721 2014 2314.49643 2015 2432.75179