Year	billion cubic meters
1961	38
1962	38
1963	38
1964	38
1965	38
1966	38
1967	38
1968	38
1969	38
1970	38
1971	38
1972	38
1973	38
1974	38
1975	38
1976	38
1977	38
1978	38
1979	38
1980	38
1981	38
1982	38
1983	38
1984	38
1985	38
1986	38
1987	38
1988	38
1989	38
1990	38
1991	38
1992	38
1993	38
1994	38
1995	38
1996	38
1997	38
1998	38
1999	38
2000	38
2001	38
2002	38
2003	38
2004	38
2005	38
2006	38
2007	38
2008	38
2009	38
2010	38
2011	38
2012	38
2013	38
2014	38
2015	38
2016	38
2017	38
2018	38
2019	38
2020	38