Year	US Dollars
1970	603180000
1971	676472000
1972	753134000
1973	881777000
1974	1008319000
1975	1115792000
1976	1290715000
1977	2248217000
1978	2954539000
1979	3410541000
1980	3533401000
1981	3611173000
1982	3777324000
1983	4063243000
1984	4097301000
1985	4886590000
1986	5944695000
1987	6817910000
1988	6800241000
1989	6974801000
1990	7689860000
1991	8251262000
1992	8542690000
1993	8693830000
1994	9614054000
1995	10819486000
1996	11379075000
1997	11229239000
1998	10845589000
1999	11912140000
2000	11355173000
2001	12916183000
2002	15490954000
2003	18109298000
2004	19558062000
2005	17922223000
2006	18665139000
2007	20504800000
2008	21381015000
2009	22721908000
2010	22471865000
2011	22641825000
2012	25261471000
2013	25661397000
2014	26371914000
2015	27130593000
2016	28110513000