Year	US Dollars
1970	385063000
1971	395964000
1972	452075000
1973	564427000
1974	1136484000
1975	1598562000
1976	2087108000
1977	2620859000
1978	3159017000
1979	4077983000
1980	5176870000
1981	6193990000
1982	7169373000
1983	7506205000
1984	8480411000
1985	8955220000
1986	9631221000
1987	11248634000
1988	11530982000
1989	13359369000
1990	14798046000
1991	15298883000
1992	15558411000
1993	15979636000
1994	17096154000
1995	17816474000
1996	16971981000
1997	16326143000
1998	16843013000
1999	16203845000
2000	16076004000
2001	15030792000
2002	16130971000
2003	17297666000
2004	18335821000
2005	17563364000
2006	18453917000
2007	19743364000
2008	20291672000
2009	21067009000
2010	22286340000
2011	21148417000
2012	21796532000
2013	22471572000
2014	21762241000
2015	21403615000
2016	21082004000