Year	US Dollars adjusted for inflation)
1987	10.76
1988	11.42
1989	12.21
1990	12.66
1991	13.09
1992	14.04
1993	14.53
1994	15.12
1995	15.68
1996	16.1
1997	16.88
1998	17.16
1999	17.88
2000	17.31
2001	17.31
2002	17.53
2003	17.45
2004	17.28
2005	17.49
2006	17.94