Year	US Dollars
1970	939559000
1971	1260811000
1972	1549797000
1973	2991380000
1974	3365978000
1975	4632813000
1976	6114380000
1977	10598950000
1978	15733603000
1979	18505558000
1980	19363274000
1981	18370310000
1982	17639482000
1983	16367460000
1984	15890301000
1985	18260736000
1986	22649742000
1987	24448828000
1988	26101338000
1989	27248507000
1990	28153909000
1991	28489963000
1992	27351236000
1993	26274671000
1994	30241912000
1995	33051440000
1996	33653884000
1997	30902557000
1998	30692715000
1999	28206747000
2000	25476934000
2001	22763886000
2002	23045302000
2003	23774850000
2004	22426650000
2005	17092402000
2006	5910801000
2007	6134509000
2008	6246392000
2009	7420897000
2010	7260316000
2011	6064669000
2012	5515626000
2013	5245583000
2014	5521298000
2015	4671372000
2016	5466348000