Year kt 1960 0 1961 0 1962 0 1963 0 1964 0 1965 0 1966 0 1967 0 1968 0 1969 0 1970 0 1971 0 1972 0 1973 0 1974 0 1975 0 1976 0 1977 0 1978 0 1979 0 1980 0 1981 18.335 1982 40.337 1983 135.679 1984 117.344 1985 73.34 1986 77.007 1987 77.007 1988 55.005 1989 14.668 1990 7.334 1991 3.667 1992 0 1993 0 1994 0 1995 425.372 1996 627.057 1997 1140.437 1998 1899.506 1999 2159.863 2000 3065.612 2001 2566.9 2002 4103.373 2003 5210.807 2004 8767.797 2005 9402.188 2006 11221.02 2007 12489.802 2008 13912.598 2009 15386.732 2010 18063.642 2011 16292.481 2012 17971.967 2013 18734.703 2014 19614.783 2015 20480.195 2016 20384.853