Year	US Dollars
1960	0.03165
1961	0.02561
1962	0.00528
1963	-0.02197
1964	0.05568
1965	0.07189
1966	0.0887
1967	0.08819
1968	0.07602
1969	0.15041
1970	0.20519
1971	0.27477
1972	0.38934
1973	0.55819
1974	1.61796
1975	2.06321
1976	4.75582
1977	4.64511
1978	4.93218
1979	4.9004
1980	4.61612
1981	2.77909
1982	3.54228
1983	3.68969
1984	3.55371
1985	4.13734
1986	4.08188
1987	4.73326
1988	5.87601
1989	5.39935
1990	4.87546
1991	3.44695
1992	2.29976
1993	4.04947
1994	4.32802
1995	5.82335
1996	5.21936
1997	5.94647
1998	7.26407
1999	5.3649
2000	4.05824
2001	4.90613
2002	5.5604
2003	6.83441
2004	8.86124
2005	8.01521
2006	7.30066
2007	8.56708
2008	11.13012
2009	9.97591
2010	11.73119
2011	7.72478
2012	7.58315
2013	8.78499
2014	23.07972
2015	49.20328
2016	237.88637
2017	64.81067
2018	66.18678
2019	43.92978
2020	46.82011
2021	13.49014