Year Measure 1960 3033.05065 1961 3006.74739 1962 3087.34197 1963 3196.83118 1964 3212.53456 1965 3329.41016 1966 3306.78161 1967 3345.55349 1968 3406.14449 1969 3557.12928 1970 3684.95235 1971 3733.283 1972 3747.96248 1973 3880.65017 1974 3734.84165 1975 3545.81713 1976 3616.97553 1977 3695.38387 1978 3675.43527 1979 3858.97596 1980 3523.64884 1981 3415.37757 1982 3397.12229 1983 3377.90491 1984 3370.52494 1985 3550.78379 1986 3597.94469 1987 3619.07727 1988 3643.00688 1989 3626.29786 1990 3597.05162 1991 3707.95197 1992 3684.72454 1993 3713.18582 1994 3732.52111 1995 3728.96315 1996 3879.82279 1997 3760.71237 1998 3787.10845 1999 3784.07409 2000 3785.75313 2001 3784.92817 2002 3685.86949 2003 3731.60972 2004 3694.4786 2005 3686.3599 2006 3598.81041 2007 3441.64022 2008 3361.98052 2009 3145.58566 2010 3230.61598 2011 2972.14799 2012 3042.85581 2013 2987.70278 2014 2776.8441 2015 2763.98006