Year	US Dollars adjusted for inflation)
1980	6.88
1981	6.97
1982	7.57
1983	7.62
1984	8.13
1985	8.05
1986	8.24
1987	8.22
1988	8.45
1989	8.42
1990	8.18
1991	7.82
1992	8.56
1993	9.17
1994	9.11
1995	9.3
1996	9.41
1997	9.77
1998	10.06
1999	10.09
2000	10.48
2001	9.68
2002	10.06
2003	10.49
2004	11.08
2005	11.54
2006	11.94