Year	US Dollars
1970	3432690000
1971	4682279000
1972	5814545000
1973	7270798000
1974	9100923000
1975	11497813000
1976	14010055000
1977	16470547000
1978	18045709000
1979	18623753000
1980	20937702000
1981	22761141000
1982	25133287000
1983	30229381000
1984	32025242000
1985	36714624000
1986	42914289000
1987	52526345000
1988	54053868000
1989	59380148000
1990	69848499000
1991	79523030000
1992	87978588000
1993	89146947000
1994	107808954000
1995	124388680000
1996	128988712000
1997	136322465000
1998	151466804000
1999	151788588000
2000	144031659000
2001	132693891000
2002	128429103000
2003	134358681000
2004	138028986000
2005	142120094000
2006	135959423000
2007	147817590000
2008	157906449000
2009	179394964000
2010	198268605000
2011	219619633000
2012	252555891000
2013	265452911000
2014	292970691000
2015	308221474000
2016	316430908000