Year	metric tons
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	1
1969	4
1970	8
1971	10
1972	15
1973	20
1974	20
1975	30
1976	70
1977	120
1978	163
1979	230
1980	509
1981	816
1982	1122
1983	1375
1984	2055
1985	2810
1986	2573
1987	1982
1988	3040
1989	2662
1990	2729
1991	3169
1992	5116
1993	4635
1994	4521
1995	5857
1996	6355
1997	5596
1998	7233
1999	6079
2000	6797
2001	5880
2002	5988
2003	7217
2004	8692
2005	8533
2006	8902
2007	8425
2008	8595
2009	8697
2010	8610
2011	7500
2012	6200
2013	4000
2014	3000
2015	2500
2016	2500
2017	2350
2018	2225
2019	2150
2020	1855
2021	1805
2022	1755