Year	billion cubic meters
1980	517.6
1981	512.35
1982	507.1
1983	501.85
1984	496.6
1985	491.35
1986	486.1
1987	480.85
1988	475.6
1989	470.35
1990	465.1
1991	465.95
1992	466.8
1993	467.65
1994	468.5
1995	469.35
1996	470.2
1997	471.05
1998	471.9
1999	472.75
2000	473.5
2001	474.6
2002	475.6
2003	476.6
2004	477.6
2005	478.6
2006	466.64
2007	454.68
2008	442.72
2009	430.76
2010	418.7
2011	423.9192223549
2012	429.0384447098
2013	434.1576670647
2014	439.2768894196
2015	444.3961117745
2016	444.3961117745
2017	444.3961117745
2018	444.3961117745
2019	444.3961117745
2020	444.3961117745