Year	billion cubic meters
1987	0.01
1988	0.0105692308
1989	0.0111384615
1990	0.0117076923
1991	0.0122769231
1992	0.0128461538
1993	0.0134153846
1994	0.0139846154
1995	0.0145538462
1996	0.0151230769
1997	0.0156923077
1998	0.0162615385
1999	0.0168307692
2000	0.0174
2001	0.01788
2002	0.01836
2003	0.01884
2004	0.01932
2005	0.0198
2006	0.0198
2007	0.0198
2008	0.0198
2009	0.0198
2010	0.0198
2011	0.0198
2012	0.0198
2013	0.0198
2014	0.0198
2015	0.0198
2016	0.0198
2017	0.0198
2018	0.0198
2019	0.0198
2020	0.0198