Year US Dollars adjusted for inflation) 1991 17.95 1992 17.67 1993 17.3 1994 17.31 1995 17.22 1996 17.72 1997 18.34 1998 18.98 1999 20.01 2000 20.47 2001 20.81 2002 22.21 2003 24.6 2004 24.85 2005 26.52