Year	US Dollars
1991	0.04343
1992	4.17564
1993	21.33534
1994	36.66609
1995	44.8846
1996	68.87594
1997	55.64019
1998	49.17279
1999	59.37662
2000	42.17426
2001	73.26923
2002	79.73075
2003	57.86571
2004	80.0058
2005	75.1678
2006	92.05105
2007	98.94154
2008	212.58174
2009	208.17587
2010	155.50764
2011	145.10011
2012	176.77991
2013	173.84823
2014	151.57227
2015	120.50919
2016	124.14202
2017	120.02133
2018	158.08191
2019	132.30341
2020	279.59694
2021	206.98861