Year	metric tons
1960	200
1961	300
1962	300
1963	300
1964	300
1965	300
1966	300
1967	400
1968	400
1969	400
1970	400
1971	500
1972	500
1973	500
1974	500
1975	600
1976	600
1977	600
1978	600
1979	600
1980	700
1981	700
1982	700
1983	800
1984	800
1985	800
1986	800
1987	1000
1988	1000
1989	1000
1990	1100
1991	1100
1992	1200
1993	1200
1994	1300
1995	1300
1996	1300
1997	1250
1998	1200
1999	1200
2000	1000
2001	800
2002	900
2003	900
2004	1000
2005	1000
2006	1000
2007	1000
2008	1000
2009	1000
2010	1000
2011	1150
2012	1300
2013	1450
2014	1600
2015	1750
2016	1900
2017	2000
2018	2050
2019	2100
2020	2000
2021	1800
2022	2000