Year metric tons 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 5 1973 10 1974 15 1975 25 1976 40 1977 60 1978 90 1979 130 1980 170 1981 200 1982 220 1983 250 1984 272 1985 270 1986 271 1987 252 1988 254 1989 1180 1990 1070 1991 1230 1992 1230 1993 1135 1994 1235 1995 1161 1996 1161 1997 1150 1998 1150 1999 1135 2000 1100 2001 1135 2002 1135 2003 1100 2004 1205 2005 1214 2006 1214 2007 1216 2008 1216 2009 1249 2010 1261 2011 1466 2012 1471 2013 1593 2014 1593 2015 1593 2016 1733 2017 1733 2018 1843 2019 2358.1 2020 2358.1 2021 2364 2022 2500