Year	US Dollars adjusted for inflation)
1977	4049.73964
1978	4250.24928
1979	4593.78386
1980	5002.58482
1981	5086.49733
1982	5136.19746
1983	5227.0804
1984	5711.06141
1985	6244.51113
1986	6957.73685
1987	7461.42335
1988	8231.44739
1989	8737.69726
1990	9169.08224
1991	8932.93893
1992	9236.65143
1993	9769.15992
1994	10160.25427
1995	10614.98993
1996	11114.89831
1997	11753.2449
1998	11550.73425
1999	11807.05456
2000	12911.31434
2001	13434.37428
2002	13588.91802
2003	12913.53267
2004	13193.8112
2005	14162.15458
2006	14243.26742
2007	14054.4723
2008	14775.82207
2009	14173.57874
2010	13704.25445
2011	13881.60578
2012	13644.75396
2013	14335.88509
2014	15029.61654
2015	15469.21325
2016	15657.22406
2017	15779.31964