Year	billion cubic meters
1980	3.34
1981	3.3874
1982	3.4348
1983	3.4822
1984	3.5296
1985	3.577
1986	3.6226
1987	3.6682
1988	3.7138
1989	3.7594
1990	3.805
1991	3.7334
1992	3.6618
1993	3.5902
1994	3.5186
1995	3.447
1996	3.5445
1997	3.642
1998	3.654
1999	3.666
2000	3.636
2001	3.607
2002	3.577
2003	3.566125
2004	3.55525
2005	3.544375
2006	3.5335
2007	3.522625
2008	3.51175
2009	3.500875
2010	3.49
2011	3.49
2012	3.49
2013	3.49
2014	3.49
2015	3.49
2016	3.49
2017	3.49
2018	3.49
2019	3.49
2020	3.49