Year US Dollars adjusted for inflation) 1960 4506.05043 1961 4717.32419 1962 4993.18686 1963 5265.18038 1964 5594.34889 1965 6036.75714 1966 6330.49059 1967 6851.41434 1968 7491.48044 1969 7719.31832 1970 8770.31069 1971 9391.60693 1972 10160.07331 1973 11294.57549 1974 11265.41683 1975 10373.80328 1976 10778.66307 1977 11262.3327 1978 11455.21025 1979 11972.13153 1980 12386.89062 1981 12478.65289 1982 12667.44163 1983 12586.97777 1984 12302.94272 1985 12613.78958 1986 13124.17865 1987 13965.44672 1988 15026.94681 1989 16018.1349 1990 16687.26509 1991 17456.38673 1992 17660.29538 1993 17278.29946 1994 17398.12751 1995 18080.54707 1996 18642.53929 1997 19380.97543 1998 20207.28368 1999 20874.57846 2000 21513.45973 2001 21777.40814 2002 21824.97562 2003 21540.06971 2004 21877.90694 2005 22004.79943 2006 22306.28405 2007 22817.3218 2008 22829.848 2009 22128.84552 2010 22538.65408 2011 22159.47542 2012 21353.23026 2013 21228.08936 2014 21533.49011 2015 22016.83692 2016 22444.07108 2017 23116.57933