Year	US Dollars adjusted for inflation)
1980	4.51
1981	4.7
1982	4.73
1983	5.28
1984	5.8
1985	5.96
1986	6.56
1987	6.75
1988	7.24
1989	7.55
1990	8.17
1991	8.72
1992	9.13
1993	9.6
1994	10.1
1995	10.66
1996	11.21
1997	11.78
1998	12.13
1999	13.01
2000	13.44
2001	13.77
2002	14.57
2003	15.23
2004	15.92
2005	16.65
2006	17.62