Year US Dollars 1970 37033000 1971 34634000 1972 32581000 1973 36935000 1974 36186000 1975 33745000 1976 40781000 1977 61097000 1978 148245000 1979 183129000 1980 207636000 1981 185847000 1982 205659000 1983 237054000 1984 191399000 1985 236548000 1986 273384000 1987 302734000 1988 259450000 1989 271308000 1990 256770000 1991 260466000 1992 237879000 1993 228075000 1994 240650000 1995 249458000 1996 234630000 1997 408840000 1998 301144000 1999 341611000 2000 334314000 2001 342241000 2002 391008000 2003 423425000 2004 426174000 2005 475237000 2006 431103000 2007 429288000 2008 432826000 2009 516295000 2010 701721000 2011 643917000 2012 480209000 2013 458031000 2014 416586000 2015 390848000 2016 497239000