Year	billion cubic meters
1980	0.657
1981	0.67625
1982	0.6955
1983	0.71475
1984	0.734
1985	0.75325
1986	0.7725
1987	0.79175
1988	0.811
1989	0.83025
1990	0.8495
1991	0.86875
1992	0.888
1993	0.90725
1994	0.9265
1995	0.94575
1996	0.965
1997	0.98425
1998	1.0035
1999	1.02275
2000	1.042
2001	1.0472
2002	1.0524
2003	1.0576
2004	1.0628
2005	1.068
2006	1.068
2007	1.068
2008	1.068
2009	1.068
2010	1.068
2011	1.068
2012	1.068
2013	1.068
2014	1.068
2015	1.068
2016	1.068
2017	1.068
2018	1.068
2019	1.068
2020	1.068