Year	US Dollars adjusted for inflation)
1981	227.78344
1982	223.57766
1983	234.72672
1984	220.92715
1985	190.14025
1986	201.97453
1987	222.7096
1988	216.66397
1989	208.78687
1990	207.21978
1991	185.7299
1992	163.62328
1993	178.60865
1994	177.99487
1995	182.70888
1996	199.00502
1997	199.1113
1998	186.6614
1999	190.69155
2000	196.50496
2001	206.74314
2002	203.90591
2003	193.86692
2004	214.04483
2005	232.7832
2006	251.05605
2007	272.3912
2008	293.85331
2009	311.36774
2010	341.30991
2011	369.58442
2012	391.1318
2013	421.38414
2014	452.77824
2015	487.29001
2016	511.18743
2017	549.84787