Year	billion cubic meters
1961	0.4
1962	0.4
1963	0.4
1964	0.4
1965	0.4
1966	0.4
1967	0.4
1968	0.4
1969	0.4
1970	0.4
1971	0.4
1972	0.4
1973	0.4
1974	0.4
1975	0.4
1976	0.4
1977	0.4
1978	0.4
1979	0.4
1980	0.4
1981	0.4
1982	0.4
1983	0.4
1984	0.4
1985	0.4
1986	0.4
1987	0.4
1988	0.4
1989	0.4
1990	0.4
1991	0.4
1992	0.4
1993	0.4
1994	0.4
1995	0.4
1996	0.4
1997	0.4
1998	0.4
1999	0.4
2000	0.4
2001	0.4
2002	0.4
2003	0.4
2004	0.4
2005	0.4
2006	0.4
2007	0.4
2008	0.4
2009	0.4
2010	0.4
2011	0.4
2012	0.4
2013	0.4
2014	0.4
2015	0.4
2016	0.4
2017	0.4
2018	0.4
2019	0.4
2020	0.4