Year US Dollars adjusted for inflation) 1970 2249.08258 1971 2399.50956 1972 2472.0338 1973 2514.928 1974 2501.70362 1975 2703.06448 1976 2818.1867 1977 3034.88848 1978 3209.5153 1979 3222.57349 1980 3048.24929 1981 3630.29894 1982 3937.56108 1983 4133.52081 1984 4438.8836 1985 4480.27001 1986 4447.00818 1987 4297.29531 1988 4409.31218 1989 4394.01891 1990 4225.94398 1991 3745.23053 1992 3289.982 1993 2784.7255 1994 2790.09867 1995 2844.12054 1996 3051.68284 1997 3121.53877 1998 3112.3453 1999 3291.30449 2000 3473.24349 2001 3572.39606 2002 3613.13636 2003 3741.20641 2004 3949.3478 2005 4385.00248 2006 4908.87933 2007 5261.89673 2008 5475.58107 2009 5550.70597 2010 5676.1414 2011 5824.10363 2012 5985.20153 2013 6133.47373 2014 6182.7737 2015 6444.98011