Year	mm per year
1961	2875
1962	2875
1963	2875
1964	2875
1965	2875
1966	2875
1967	2875
1968	2875
1969	2875
1970	2875
1971	2875
1972	2875
1973	2875
1974	2875
1975	2875
1976	2875
1977	2875
1978	2875
1979	2875
1980	2875
1981	2875
1982	2875
1983	2875
1984	2875
1985	2875
1986	2875
1987	2875
1988	2875
1989	2875
1990	2875
1991	2875
1992	2875
1993	2875
1994	2875
1995	2875
1996	2875
1997	2875
1998	2875
1999	2875
2000	2875
2001	2875
2002	2875
2003	2875
2004	2875
2005	2875
2006	2875
2007	2875
2008	2875
2009	2875
2010	2875
2011	2875
2012	2875
2013	2875
2014	2875
2015	2875
2016	2875
2017	2875
2018	2875
2019	2875
2020	2875