Year	US Dollars adjusted for inflation)
1980	13.36
1981	13.77
1982	14.06
1983	14.21
1984	14.59
1985	15.23
1986	15.52
1987	16.01
1988	16.76
1989	17.41
1990	18.29
1991	18.85
1992	19.15
1993	19.76
1994	20.04
1995	20.58
1996	20.96
1997	21.37
1998	21.32
1999	21.84
2000	22.39
2001	22.7
2002	23.19
2003	23.57
2004	24.33
2005	24.84
2006	25.15