Year	US Dollars
1970	572133000
1971	542384000
1972	601811000
1973	756432000
1974	730062000
1975	720586000
1976	710689000
1977	1066621000
1978	1278643000
1979	1281957000
1980	1398362000
1981	1538841000
1982	1484228000
1983	1666170000
1984	1963070000
1985	2256459000
1986	2766883000
1987	3313213000
1988	3131102000
1989	3402452000
1990	3880930000
1991	4380167000
1992	4508058000
1993	4886541000
1994	5469146000
1995	5935784000
1996	6442987000
1997	6347318000
1998	6969087000
1999	7103698000
2000	6743347000
2001	6860996000
2002	7640293000
2003	8301007000
2004	7239724000
2005	7334163000
2006	3697633000
2007	5041282000
2008	5461776000
2009	7385000000
2010	9114078000
2011	11224506000
2012	12837232000
2013	16626329000
2014	18361454000
2015	20630861000
2016	21396063000