Year Measure 1960 4251.43591 1961 4307.82075 1962 4451.56012 1963 4694.12007 1964 4903.60761 1965 5153.93241 1966 5272.6647 1967 5557.29174 1968 5871.52039 1969 6091.10001 1970 6476.38853 1971 6530.33556 1972 6933.60655 1973 7123.37922 1974 7100.54809 1975 7150.10681 1976 7272.55005 1977 7409.53001 1978 7538.84294 1979 7837.76966 1980 7804.2201 1981 7530.94526 1982 7149.34406 1983 7051.62956 1984 7341.51922 1985 7439.34207 1986 7492.11338 1987 7641.32411 1988 7854.97204 1989 7933.56708 1990 7602.67493 1991 7481.50384 1992 7562.14813 1993 7730.48665 1994 7926.83925 1995 7965.84677 1996 8036.71332 1997 8034.41478 1998 7924.03092 1999 8081.48696 2000 8242.52466 2001 8040.5389 2002 7993.38974 2003 8332.92385 2004 8441.18487 2005 8404.24591 2006 8240.11562 2007 8213.66351 2008 8195.21231 2009 7797.19626 2010 7788.47261 2011 7910.75935 2012 7725.32831 2013 7728.43407 2014 7876.09411 2015 7603.73926