Year	US Dollars adjusted for inflation)
1980	22.87
1981	23.4
1982	23.3
1983	23.85
1984	24.36
1985	24.74
1986	25.3
1987	25.5
1988	25.8
1989	25.98
1990	26.39
1991	26.71
1992	27.58
1993	27.67
1994	27.92
1995	27.95
1996	28.64
1997	29.08
1998	29.65
1999	30.38
2000	31.1
2001	31.7
2002	32.64
2003	33.62
2004	34.53
2005	35.11
2006	35.63