Year US Dollars 1970 0 1971 48816000 1972 99160000 1973 258063000 1974 375393000 1975 440332000 1976 535433000 1977 723294000 1978 926936000 1979 1175002000 1980 1685753000 1981 2041164000 1982 2404746000 1983 2797978000 1984 3003217000 1985 3340617000 1986 3883335000 1987 4587003000 1988 5247813000 1989 5594815000 1990 6354024000 1991 6475142000 1992 6573076000 1993 5944864000 1994 6153590000 1995 6250656000 1996 6399961000 1997 3917094000 1998 5778378000 1999 5132267000 2000 5152421000 2001 5187678000 2002 5323448000 2003 5480632000 2004 5603366000 2005 5477561000 2006 5713773000 2007 6155424000 2008 6228634000 2009 6799205000 2010 6492701000 2011 6417662000 2012 7718089000 2013 7569770000 2014 7818019000 2015 7287189000 2016 7065832000