Year	metric tons
1961	400
1962	400
1963	400
1964	400
1965	400
1966	420
1967	430
1968	440
1969	460
1970	470
1971	480
1972	500
1973	520
1974	530
1975	550
1976	500
1977	500
1978	500
1979	450
1980	450
1981	500
1982	500
1983	600
1984	700
1985	728
1986	900
1987	1200
1988	1500
1989	2000
1990	2700
1991	3600
1992	4000
1993	4000
1994	4300
1995	4000
1996	4500
1997	4000
1998	1352
1999	1487
2000	2230
2001	2500
2002	2550
2003	2600
2004	2650
2005	2757.64
2006	2700
2007	3000
2008	2800
2009	2000
2010	1561.17
2011	1084.5
2012	917.4
2013	776.1
2014	829.6
2015	823.25
2016	768
2017	576
2018	941
2019	1175.85
2020	661.72
2021	593.71
2022	531.85