Year Measure 1960 873.91031 1961 962.90711 1962 1003.75225 1963 1136.48487 1964 1260.47455 1965 1361.58724 1966 1476.99749 1967 1720.54974 1968 1938.45683 1969 2193.61013 1970 2458.35709 1971 2531.08854 1972 2667.04675 1973 2964.20822 1974 2924.24571 1975 2725.15933 1976 2876.80085 1977 2899.90422 1978 2898.33881 1979 3044.05284 1980 2950.13535 1981 2864.36865 1982 2840.60844 1983 2823.8771 1984 3017.8152 1985 3005.2381 1986 3020.56048 1987 3044.11509 1988 3242.67869 1989 3350.72629 1990 3551.16177 1991 3575.24609 1992 3649.94432 1993 3664.56836 1994 3850.96244 1995 3935.99475 1996 4008.47624 1997 4041.16767 1998 3955.62763 1999 4011.22478 2000 4083.8317 2001 4008.26803 2002 3991.97757 2003 3953.18451 2004 4078.21054 2005 4062.97905 2006 4053.88344 2007 4012.65424 2008 3858.43452 2009 3678.51113 2010 3893.2666 2011 3610.81217 2012 3537.36317 2013 3567.62935 2014 3470.76313 2015 3428.55722