Year	billion cubic meters
1961	67
1962	67
1963	67
1964	67
1965	67
1966	67
1967	67
1968	67
1969	67
1970	67
1971	67
1972	67
1973	67
1974	67
1975	67
1976	67
1977	67
1978	67
1979	67
1980	67
1981	67
1982	67
1983	67
1984	67
1985	67
1986	67
1987	67
1988	67
1989	67
1990	67
1991	67
1992	67
1993	67
1994	67
1995	67
1996	67
1997	67
1998	67
1999	67
2000	67
2001	67
2002	67
2003	67
2004	67
2005	67
2006	67
2007	67
2008	67
2009	67
2010	67
2011	67
2012	67
2013	67
2014	67
2015	67
2016	67
2017	67
2018	67
2019	67
2020	67