Year	US Dollars adjusted for inflation)
1980	20.01
1981	20.06
1982	20.25
1983	21.09
1984	22.24
1985	22.86
1986	22.99
1987	23.41
1988	23.49
1989	24.46
1990	25.32
1991	26.41
1992	27.22
1993	27.84
1994	28.89
1995	29.83
1996	30.83
1997	31.68
1998	31.72
1999	32.11
2000	33.39
2001	34.55
2002	35.31
2003	36.44
2004	37.17
2005	37.7
2006	37.99