Year	billion cubic meters
1961	0.6
1962	0.6
1963	0.6
1964	0.6
1965	0.6
1966	0.6
1967	0.6
1968	0.6
1969	0.6
1970	0.6
1971	0.6
1972	0.6
1973	0.6
1974	0.6
1975	0.6
1976	0.6
1977	0.6
1978	0.6
1979	0.6
1980	0.6
1981	0.6
1982	0.6
1983	0.6
1984	0.6
1985	0.6
1986	0.6
1987	0.6
1988	0.6
1989	0.6
1990	0.6
1991	0.6
1992	0.6
1993	0.6
1994	0.6
1995	0.6
1996	0.6
1997	0.6
1998	0.6
1999	0.6
2000	0.6
2001	0.6
2002	0.6
2003	0.6
2004	0.6
2005	0.6
2006	0.6
2007	0.6
2008	0.6
2009	0.6
2010	0.6
2011	0.6
2012	0.6
2013	0.6
2014	0.6
2015	0.6
2016	0.6
2017	0.6
2018	0.6
2019	0.6
2020	0.6