Year US Dollars 1970 0 1971 0 1972 0 1973 0 1974 0 1975 0 1976 0 1977 0 1978 0 1979 0 1980 4618943000 1981 3969212000 1982 8269751000 1983 7078087000 1984 5159731000 1985 6025227000 1986 5793966000 1987 6150724000 1988 5843050000 1989 6526858000 1990 9026182000 1991 11368429000 1992 16074663000 1993 23392441000 1994 21792479000 1995 21681653000 1996 16684173000 1997 11697339000 1998 12341636000 1999 9742307000 2000 8130251000 2001 7647084000 2002 8934508000 2003 14235372000 2004 20950355000 2005 21393523000 2006 20494229000 2007 20834060000 2008 16026647000 2009 18609982000 2010 19768743000 2011 17260285000 2012 7471977000 2013 6993578000 2014 5758232000 2015 6321580000 2016 5378273000