Year	US Dollars adjusted for inflation)
1980	19.78
1981	20.35
1982	21.8
1983	22.28
1984	22.65
1985	23.44
1986	24.02
1987	24.38
1988	25.09
1989	25.79
1990	26.39
1991	26.8
1992	27.43
1993	27.7
1994	28.33
1995	29.13
1996	29.25
1997	29.88
1998	30.67
1999	31.17
2000	32.36
2001	32.65
2002	33.67
2003	34.11
2004	34.26
2005	34.88
2006	35.18