Year	US Dollars adjusted for inflation)
1980	16.07
1981	16.24
1982	15.6
1983	15.22
1984	15.68
1985	15.12
1986	14.77
1987	14.46
1988	14.2
1989	13.91
1990	13.79
1991	14.62
1992	14.99
1993	14.55
1994	13.67
1995	13.73
1996	13.23
1997	13.73
1998	13.36
1999	12.18
2000	12.25
2001	12.35
2002	11.32
2003	10.36
2004	12.12
2005	13.54