Year	US Dollars adjusted for inflation)
1980	21.74
1981	22.17
1982	22.98
1983	23.2
1984	23.51
1985	23.53
1986	23.92
1987	24.47
1988	25.22
1989	25.91
1990	26.24
1991	27.16
1992	27.9
1993	28.48
1994	29.49
1995	29.21
1996	29.96
1997	30.57
1998	30.57
1999	31.31
2000	31.89
2001	31.73
2002	32.21
2003	32.58
2004	33.76
2005	33.46
2006	34.01