Year	metric tons
1960	100
1961	100
1962	100
1963	150
1964	150
1965	150
1966	150
1967	150
1968	150
1969	150
1970	150
1971	150
1972	150
1973	150
1974	150
1975	150
1976	150
1977	150
1978	150
1979	150
1980	150
1981	145
1982	140
1983	135
1984	130
1985	125
1986	120
1987	115
1988	110
1989	105
1990	100
1991	95
1992	90
1993	85
1994	80
1995	75
1996	70
1997	65
1998	60
1999	55
2000	50
2001	45
2002	40
2003	35
2004	30
2005	25
2006	20
2007	15
2008	10
2009	8
2010	6
2011	4
2012	2
2013	3
2014	5
2015	7
2016	12
2017	16
2018	0
2019	0.5
2020	0.5
2021	1.1
2022	9