Year	metric tons
1960	400
1961	400
1962	500
1963	500
1964	500
1965	500
1966	600
1967	600
1968	800
1969	800
1970	800
1971	1100
1972	1200
1973	1200
1974	1200
1975	1200
1976	1600
1977	1500
1978	1000
1979	1000
1980	1250
1981	1450
1982	1400
1983	1250
1984	1500
1985	1500
1986	1700
1987	1900
1988	1900
1989	1600
1990	1300
1991	1000
1992	800
1993	600
1994	400
1995	200
1996	81
1997	160
1998	191
1999	157
2000	166
2001	118
2002	139
2003	122
2004	161
2005	132
2006	81
2007	122
2008	86
2009	73
2010	60
2011	234
2012	378
2013	431
2014	1168
2015	81
2016	38
2017	38
2018	38
2019	38
2020	33
2021	38
2022	38