Year US Dollars adjusted for inflation) 1985 1374.25583 1986 1376.99087 1987 1316.46537 1988 1452.33399 1989 1318.72397 1990 1277.5869 1991 1161.16902 1992 809.10958 1993 665.3956 1994 515.76337 1995 445.15625 1996 365.43773 1997 366.34296 1998 380.15958 1999 388.21722 2000 413.58644 2001 447.78218 2002 486.86546 2003 529.80521 2004 572.53904 2005 598.30223 2006 626.79722 2007 661.34419 2008 698.23022 2009 708.94535 2010 738.34752 2011 775.2993 2012 814.77507 2013 855.51354 2014 892.64005 2015 925.62164 2016 968.3856 2017 1015.47219