Year	US Dollars adjusted for inflation)
1980	10.51
1981	10.8
1982	11.12
1983	10.69
1984	10.71
1985	11.14
1986	11.67
1987	12
1988	12.6
1989	12.78
1990	12.61
1991	13.31
1992	13.83
1993	13.93
1994	14.31
1995	14.49
1996	15.17
1997	15.83
1998	16.18
1999	16.39
2000	17.15
2001	16.46
2002	16.52
2003	16.7
2004	16.35
2005	16.54
2006	16.57