Year metric tons 1960 19233498 1961 20644548 1962 21414109 1963 21699819.1 1964 22510978.1 1965 24088392.4 1966 25727212.8 1967 26626261 1968 28067999 1969 27065424 1970 29115879 1971 30438542 1972 30434566 1973 31581356 1974 32578886 1975 32115357 1976 34355698 1977 34598825.5 1978 35013918.099999994 1979 35591755.699999996 1980 36536701.9 1981 38005656.95 1982 38084349.099999994 1983 39820966.24 1984 42292837.46999999 1985 42308433.879999995 1986 44249860.27 1987 44153881.23 1988 45237080.24 1989 45108864.79 1990 42136773.519999996 1991 41003815.00999999 1992 42909803.28999999 1993 41962558.38000001 1994 43336525.60999999 1995 42826054.65 1996 41695360.24 1997 41876456.370000005 1998 37460489.49999999 1999 38750518.02 2000 37726580.010000005 2001 37838157.04 2002 37783546.13999999 2003 36862921.97 2004 37705947.25 2005 36767095.620000005 2006 36283352.36000001 2007 36073254.71 2008 34874827.92999999 2009 34053926.57 2010 33409280.420000006 2011 33817073.27000001 2012 33195676.559999995 2013 32677462.74 2014 33870462.51 2015 33435109.74000001 2016 31761028.599999998 2017 34141941.35 2018 34275246.379999995 2019 33613175.35 2020 32683687.390000008 2021 33124432.84 2022 28369828.459999997