Year US Dollars adjusted for inflation) 1970 1186.00263 1971 1311.12729 1972 1342.36546 1973 1420.32569 1974 1457.12744 1975 1609.99335 1976 1528.02232 1977 1496.02209 1978 1469.29359 1979 1468.91392 1980 1602.42667 1981 1784.10486 1982 1754.30791 1983 1723.93662 1984 1771.87406 1985 1773.57916 1986 1912.02955 1987 2098.52708 1988 2142.10513 1989 2325.06834 1990 2720.02953 1991 2692.12171 1992 2716.37079 1993 2746.21316 1994 2759.14267 1995 2835.03905 1996 2881.07517 1997 2904.69558 1998 2916.38908 1999 2946.11067 2000 2953.2323 2001 2952.50837 2002 3059.01387 2003 3158.8261 2004 3250.39922 2005 3411.67334 2006 3568.85728 2007 3668.48073 2008 3633.31559 2009 3622.112 2010 3690.23923 2011 3704.14066 2012 3807.74132 2013 3977.97643 2014 3980.77445 2015 3923.88968 2016 3906.26188 2017 3914.01686