Year	US Dollars
1962	1060
1963	1140
1964	1240
1965	1340
1966	1470
1967	1560
1968	1680
1969	1850
1970	2070
1971	2320
1972	2760
1973	3580
1974	4650
1975	5540
1976	5980
1977	6660
1978	7540
1979	9620
1980	11460
1981	11180
1982	10380
1983	9600
1984	9270
1985	9360
1986	10820
1987	13810
1988	18070
1989	19300
1990	20630
1991	21810
1992	24520
1993	24870
1994	26140
1995	28190
1996	30090
1997	29560
1998	27970
1999	27080
2000	26790
2001	25290
2002	24970
2003	28020
2004	33750
2005	38720
2006	41460
2007	44510
2008	49110
2009	49000
2010	49610
2011	50590
2012	50060
2013	50700
2014	50420
2015	47630
2016	45850
2017	45440