Year	US Dollars
1970	8425113000
1971	9328752000
1972	10029275000
1973	10965920000
1974	12696942000
1975	13865608000
1976	14586391000
1977	15414652000
1978	16520246000
1979	18190374000
1980	20723348000
1981	22480056000
1982	26942857000
1983	30649486000
1984	32763964000
1985	38934796000
1986	44909437000
1987	53424898000
1988	59288512000
1989	73721054000
1990	83471510000
1991	84852339000
1992	87775433000
1993	91330322000
1994	97898637000
1995	93808992000
1996	93966079000
1997	94059303000
1998	98333658000
1999	99779503000
2000	101131480000
2001	99500089000
2002	105741612000
2003	118884623000
2004	123644482000
2005	121195475000
2006	159525523000
2007	204057533000
2008	227111767000
2009	256312230000
2010	290427553000
2011	334399295000
2012	392625128000
2013	427296379000
2014	457552597000
2015	478874627000
2016	456139934000