Year	US Dollars
1960	31.1603
1961	37.75539
1962	33.75966
1963	23.55246
1964	18.70746
1965	11.81059
1966	10.06232
1967	8.34605
1968	9.06756
1969	9.72721
1970	8.85842
1971	8.5746
1972	7.63864
1973	8.45976
1974	8.46861
1975	14.96182
1976	8.81003
1977	7.53756
1978	10.79191
1979	6.10118
1980	10.94807
1981	8.6335
1982	6.73497
1983	4.51018
1984	5.65498
1985	7.77801
1986	7.31256
1987	9.04982
1988	7.094
1989	6.35649
1990	12.99667
1991	8.08031
1992	14.01173
1993	11.92901
1994	10.57701
1995	10.38485
1996	10.58768
1997	8.40988
1998	14.0309
1999	4.54688
2000	6.49756
2001	6.37352
2002	5.88527
2003	7.46322
2004	9.74987
2005	10.5405
2006	7.19843
2007	11.62347
2008	9.39641
2009	8.59159
2010	5.61267
2011	5.29095
2012	3.95378
2013	5.35307
2014	4.14394
2015	1.79879
2016	3.58335
2017	4.24635
2018	3.44909
2019	4.0276
2020	4.82421
2021	4.85265