Year	US Dollars
1973	0.15513
1974	46.71587
1975	32.16991
1976	48.60134
1977	83.90911
1978	55.96232
1979	50.76692
1980	84.76013
1981	138.9145
1982	75.88416
1983	51.52275
1984	36.1066
1985	45.35113
1986	78.03808
1987	86.39846
1988	132.06839
1989	68.20039
1990	72.79561
1991	113.61851
1992	72.22506
1993	45.56916
1994	62.0229
1995	33.1881
1996	55.44571
1997	61.08006
1998	137.5186
1999	146.84169
2000	131.6368
2001	112.57626
2002	175.01134
2003	72.11015
2004	24.06861
2005	100.91525
2006	40.54639
2007	60.84178
2008	72.91204
2009	50.39393
2010	229.41828
2011	177.7952
2012	23.83831
2013	17.96671
2014	28.57591
2015	16.56642
2016	1.98754
2017	113.039
2018	192.08522
2019	297.99061
2020	278.74903
2021	58.03538