Year	US Dollars
1970	64232000
1971	68095000
1972	61560000
1973	56394000
1974	49285000
1975	45669000
1976	39041000
1977	53178000
1978	184819000
1979	277531000
1980	510290000
1981	621068000
1982	725433000
1983	920211000
1984	866304000
1985	876003000
1986	866474000
1987	963318000
1988	993308000
1989	1031127000
1990	1787050000
1991	1562590000
1992	1814004000
1993	1352798000
1994	2126760000
1995	2974205000
1996	4017529000
1997	5092469000
1998	6972407000
1999	8490679000
2000	10073262000
2001	13541771000
2002	17483175000
2003	19007578000
2004	22749833000
2005	22721604000
2006	24133741000
2007	25807489000
2008	24267157000
2009	24706099000
2010	24675506000
2011	24826153000
2012	29134947000
2013	30917743000
2014	29942644000
2015	30895976000
2016	31960710000