Year	US Dollars adjusted for inflation)
1980	12.96
1981	13.63
1982	14.05
1983	14.21
1984	15.17
1985	15.67
1986	15.45
1987	16.18
1988	17.04
1989	17.98
1990	18.75
1991	19.48
1992	20.4
1993	20.85
1994	21.36
1995	22.33
1996	23.27
1997	25.62
1998	26.65
1999	28.05
2000	29.29
2001	29.81
2002	31.27
2003	32.55
2004	32.93
2005	33.36
2006	34.14