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