Year	US Dollars
1973	0.83245
1974	67.97886
1975	79.19496
1976	63.39214
1977	38.13321
1978	31.60217
1979	17.82979
1980	70.95114
1981	92.64863
1982	64.66234
1983	53.64372
1984	43.25359
1985	52.57964
1986	86.4921
1987	78.30092
1988	129.52545
1989	132.92324
1990	86.50677
1991	160.2573
1992	185.2206
1993	172.48224
1994	209.21753
1995	316.5122
1996	250.56993
1997	163.77835
1998	39.59071
1999	162.64786
2000	69.52978
2001	101.68499
2002	205.74911
2003	95.43261
2004	-131.94187
2005	64.57621
2006	111.97212
2007	116.04723
2008	99.00579
2009	229.77466
2010	240.73479
2011	205.0016
2012	154.80233
2013	145.76556
2014	110.80983
2015	78.34965
2016	86.3315
2017	86.81271
2018	48.12017
2019	179.80435
2020	547.599
2021	556.35647