Year	US Dollars
1960	4.9911
1961	6.6636
1962	7.90772
1963	7.46516
1964	5.29451
1965	6.03706
1966	6.30875
1967	5.98701
1968	5.15375
1969	4.95795
1970	4.9464
1971	5.59929
1972	6.25228
1973	2.18048
1974	1.29145
1975	1.47428
1976	3.11178
1977	2.2474
1978	4.1523
1979	13.50901
1980	21.61375
1981	16.16429
1982	14.09141
1983	7.56723
1984	4.99888
1985	3.66238
1986	6.76889
1987	7.39256
1988	5.39025
1989	2.71849
1990	24.0013
1991	29.10332
1992	6.32783
1993	7.81433
1994	3.40163
1995	5.2872
1996	4.08135
1997	0.11032
1998	0.4513
1999	0.19704
2000	5.12481
2001	2.04788
2002	4.14374
2003	2.50705
2004	4.26171
2005	5.81226
2006	8.17887
2007	11.34095
2008	15.72771
2009	18.82642
2010	14.35
2011	44.3022
2012	41.39855
2013	37.39894
2014	44.65776
2015	27.37537
2016	45.52451
2017	39.18695
2018	14.61541
2019	8.43019
2020	6.4537
2021	12.54419