Year	US Dollars
1970	145920000
1971	180104000
1972	221564000
1973	265900000
1974	323576000
1975	441410000
1976	610921000
1977	1112891000
1978	1529109000
1979	2172014000
1980	2572796000
1981	2646361000
1982	2802940000
1983	2895591000
1984	2895909000
1985	3161494000
1986	4137222000
1987	4588507000
1988	4812727000
1989	5364591000
1990	6562509000
1991	6767222000
1992	7514927000
1993	7745306000
1994	9358521000
1995	10953417000
1996	11074514000
1997	10751467000
1998	11317974000
1999	10765386000
2000	10561273000
2001	9748845000
2002	10285903000
2003	11408146000
2004	10855778000
2005	7700087000
2006	3418552000
2007	3088243000
2008	2838406000
2009	3240267000
2010	3190737000
2011	3094900000
2012	3739420000
2013	4915401000
2014	5162263000
2015	6611936000
2016	7283225000