Year	billion cubic meters
1961	3.5
1962	3.5
1963	3.5
1964	3.5
1965	3.5
1966	3.5
1967	3.5
1968	3.5
1969	3.5
1970	3.5
1971	3.5
1972	3.5
1973	3.5
1974	3.5
1975	3.5
1976	3.5
1977	3.5
1978	3.5
1979	3.5
1980	3.5
1981	3.5
1982	3.5
1983	3.5
1984	3.5
1985	3.5
1986	3.5
1987	3.5
1988	3.5
1989	3.5
1990	3.5
1991	3.5
1992	3.5
1993	3.5
1994	3.5
1995	3.5
1996	3.5
1997	3.5
1998	3.5
1999	3.5
2000	3.5
2001	3.5
2002	3.5
2003	3.5
2004	3.5
2005	3.5
2006	3.5
2007	3.5
2008	3.5
2009	3.5
2010	3.5
2011	3.5
2012	3.5
2013	3.5
2014	3.5
2015	3.5
2016	3.5
2017	3.5
2018	3.5
2019	3.5
2020	3.5