Year	US Dollars
1970	320105000
1971	365557000
1972	437426000
1973	520729000
1974	654054000
1975	874276000
1976	1075347000
1977	1415430000
1978	1784970000
1979	2233305000
1980	2863520000
1981	3427582000
1982	3766618000
1983	4304508000
1984	4110803000
1985	4515707000
1986	4689767000
1987	4831925000
1988	4632686000
1989	4686478000
1990	3845940000
1991	4106614000
1992	4014348000
1993	3937432000
1994	3971799000
1995	3857688000
1996	3528328000
1997	3505531000
1998	3961187000
1999	4215089000
2000	4692408000
2001	4886536000
2002	5070864000
2003	5650889000
2004	5710644000
2005	6485431000
2006	6993564000
2007	8410940000
2008	8838789000
2009	7760170000
2010	8154409000
2011	10271452000
2012	14310369000
2013	17134572000
2014	19722090000
2015	23588779000
2016	25567060000