Year US Dollars adjusted for inflation) 1984 422.95158 1985 432.16218 1986 440.59275 1987 421.95265 1988 401.62971 1989 445.53409 1990 462.00163 1991 468.4745 1992 481.08918 1993 496.20753 1994 523.43545 1995 547.35993 1996 572.85535 1997 600.19493 1998 612.59078 1999 645.99604 2000 672.16783 2001 699.63348 2002 729.8942 2003 762.74626 2004 799.07363 2005 842.56763 2006 900.27544 2007 952.31694 2008 1009.46077 2009 1067.57592 2010 1141.12712 2011 1215.88173 2012 1296.74567 2013 1383.70298 2014 1470.49971 2015 1556.67071 2016 1642.7301 2017 1730.40481