Year	US Dollars adjusted for inflation)
1980	11.66
1981	10.67
1982	10
1983	10.37
1984	10.43
1985	9.66
1986	10.52
1987	10.43
1988	10.15
1989	9.43
1990	9.36
1991	10.17
1992	11.05
1993	11.67
1994	12.36
1995	11.65
1996	12.19
1997	13.24
1998	13.73
1999	13.2
2000	12.93
2001	12.16
2002	12.18
2003	12.48
2004	12.77
2005	13.01