Year	billion cubic meters
1987	0.46
1988	0.4761538462
1989	0.4923076923
1990	0.5084615385
1991	0.5246153846
1992	0.5407692308
1993	0.5569230769
1994	0.5730769231
1995	0.5892307692
1996	0.6053846154
1997	0.6215384615
1998	0.6376923077
1999	0.6538461538
2000	0.67
2001	0.6609833333
2002	0.6519666667
2003	0.64295
2004	0.6339333333
2005	0.6249166667
2006	0.6159
2007	0.6159
2008	0.6159
2009	0.6159
2010	0.6159
2011	0.6159
2012	0.6159
2013	0.6159
2014	0.6159
2015	0.6159
2016	0.6159
2017	0.6159
2018	0.6159
2019	0.6159
2020	0.6159