Year	US Dollars
1970	477531000
1971	497896000
1972	581162000
1973	844708000
1974	1152689000
1975	1290223000
1976	1493329000
1977	1658884000
1978	2173736000
1979	2720996000
1980	3386807000
1981	3228163000
1982	3367820000
1983	3628281000
1984	3511512000
1985	4181349000
1986	4603586000
1987	5783677000
1988	5809652000
1989	5889233000
1990	7055159000
1991	7453506000
1992	6898202000
1993	7111502000
1994	7124411000
1995	7309191000
1996	6813730000
1997	6465016000
1998	6824530000
1999	6526077000
2000	6148248000
2001	5496282000
2002	6097000000
2003	6716482000
2004	6916407000
2005	6486772000
2006	6681910000
2007	7538434000
2008	7659361000
2009	8549248000
2010	8847568000
2011	10162730000
2012	11893745000
2013	13836037000
2014	16969376000
2015	19764038000
2016	22324987000