Year	billion cubic meters
1970	0.72
1971	0.817
1972	0.914
1973	1.011
1974	1.108
1975	1.205
1976	1.205
1977	1.205
1978	1.205
1979	1.205
1980	1.205
1981	1.305
1982	1.405
1983	1.505
1984	1.605
1985	1.705
1986	1.5216666667
1987	1.3383333333
1988	1.155
1989	1.2265516367
1990	1.2981032734
1991	1.2437313772
1992	1.189359481
1993	1.1349875848
1994	1.0806156886
1995	1.0262437924
1996	0.9718718962
1997	0.9175
1998	0.86468
1999	0.81186
2000	0.75904
2001	0.70622
2002	0.6534
2003	0.6453333333
2004	0.6372666667
2005	0.6292
2006	0.5923
2007	0.5554
2008	0.696
2009	0.6597
2010	0.8089
2011	0.8657
2012	0.7285
2013	1.009
2014	0.9892
2015	0.8118
2016	0.886995
2017	0.895798
2018	1.105817
2019	0.945594
2020	0.97643