Year	billion cubic meters
1961	23.5
1962	23.5
1963	23.5
1964	23.5
1965	23.5
1966	23.5
1967	23.5
1968	23.5
1969	23.5
1970	23.5
1971	23.5
1972	23.5
1973	23.5
1974	23.5
1975	23.5
1976	23.5
1977	23.5
1978	23.5
1979	23.5
1980	23.5
1981	23.5
1982	23.5
1983	23.5
1984	23.5
1985	23.5
1986	23.5
1987	23.5
1988	23.5
1989	23.5
1990	23.5
1991	23.5
1992	23.5
1993	23.5
1994	23.5
1995	23.5
1996	23.5
1997	23.5
1998	23.5
1999	23.5
2000	23.5
2001	23.5
2002	23.5
2003	23.5
2004	23.5
2005	23.5
2006	23.5
2007	23.5
2008	23.5
2009	23.5
2010	23.5
2011	23.5
2012	23.5
2013	23.5
2014	23.5
2015	23.5
2016	23.5
2017	23.5
2018	23.5
2019	23.5
2020	23.5