Year	billion cubic meters
1987	0.396
1988	0.3968
1989	0.3976
1990	0.3984
1991	0.3992
1992	0.4
1993	0.4708
1994	0.5416
1995	0.6124
1996	0.6832
1997	0.754
1998	0.8248
1999	0.8956
2000	0.9664
2001	0.9908
2002	1.0152
2003	1.0396
2004	1.064
2005	1.0884
2006	1.0884
2007	1.0884
2008	1.0884
2009	1.0884
2010	1.0884
2011	1.0884
2012	1.0884
2013	1.0884
2014	1.0884
2015	1.0884
2016	1.0884
2017	1.0884
2018	1.0884
2019	1.0884
2020	1.0884