Year	US Dollars
1970	118820000
1971	139976000
1972	158184000
1973	189110000
1974	260489000
1975	357186000
1976	381344000
1977	578774000
1978	782936000
1979	1056886000
1980	1527072000
1981	1493610000
1982	1959129000
1983	2024889000
1984	2062649000
1985	3041332000
1986	3504477000
1987	4282642000
1988	4050959000
1989	4230147000
1990	4916028000
1991	4786605000
1992	4725654000
1993	5092936000
1994	5414062000
1995	6009995000
1996	5220899000
1997	5032525000
1998	5100296000
1999	5028225000
2000	4675947000
2001	4820672000
2002	5012252000
2003	5537625000
2004	6834193000
2005	6293457000
2006	6679737000
2007	5276359000
2008	5391060000
2009	5032930000
2010	2410094000
2011	2632243000
2012	2837320000
2013	3449438000
2014	3903050000
2015	4060193000
2016	3836872000