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	60
1972	155
1973	311
1974	887
1975	1510
1976	2675
1977	3800
1978	4935
1979	7040
1980	9263
1981	11197
1982	13356
1983	15368
1984	18369
1985	17776
1986	20930
1987	24820
1988	26400
1989	26000
1990	27147
1991	20226
1992	21806
1993	21882
1994	25899
1995	28636
1996	29977
1997	30279
1998	33237
1999	31800
2000	40550
2001	62550
2002	76817
2003	91714
2004	104330
2005	111761
2006	129468
2007	158549
2008	154726
2009	179552
2010	220034
2011	247262
2012	296514
2013	325325
2014	320174
2015	346118
2016	398129
2017	412887
2018	439718
2019	458131
2020	480500
2021	478737