Year	US Dollars adjusted for inflation)
1980	5.78
1981	6.01
1982	6.27
1983	6.46
1984	6.96
1985	7.09
1986	7.52
1987	8.16
1988	8.39
1989	8.14
1990	8.75
1991	8.48
1992	8.78
1993	9.86
1994	8.78
1995	9.2
1996	9.49
1997	10.27
1998	10.29
1999	9.48
2000	10.15
2001	9.39
2002	10.21
2003	10.9
2004	11.68
2005	12.4
2006	13