Year	US Dollars adjusted for inflation)
1968	14253.52505
1969	14541.5374
1970	22133.90492
1971	25517.18414
1972	29931.47071
1973	35393.58357
1974	39125.44562
1975	33860.39159
1976	37905.11896
1977	38557.21489
1978	34657.43084
1979	36676.57982
1980	36518.04502
1981	34979.3485
1982	26017.96188
1983	20512.78435
1984	18427.00474
1985	15734.73737
1986	17509.05883
1987	15608.75271
1988	16921.54869
1989	16194.5143
1990	18002.73873
1991	20040.4957
1992	20226.85422
1993	19413.78293
1994	19041.0584
1995	18648.85687
1996	18744.78051
1997	18588.30435
1998	18763.58593
1999	17690.91757
2000	18263.23008
2001	17585.39045
2002	16619.43466
2003	17954.94979
2004	18822.73004
2005	19309.31207
2006	19304.55023
2007	19136.15923
2008	19792.72038
2009	18861.11
2010	19259.58726
2011	20575.49795
2012	21056.34715
2013	21005.01212
2014	21183.46489
2015	21507.95569
2016	21380.45272
2017	20796.31946