Year	mm per year
1961	600
1962	600
1963	600
1964	600
1965	600
1966	600
1967	600
1968	600
1969	600
1970	600
1971	600
1972	600
1973	600
1974	600
1975	600
1976	600
1977	600
1978	600
1979	600
1980	600
1981	600
1982	600
1983	600
1984	600
1985	600
1986	600
1987	600
1988	600
1989	600
1990	600
1991	600
1992	600
1993	600
1994	600
1995	600
1996	600
1997	600
1998	600
1999	600
2000	600
2001	600
2002	600
2003	600
2004	600
2005	600
2006	600
2007	600
2008	600
2009	600
2010	600
2011	600
2012	600
2013	600
2014	600
2015	600
2016	600
2017	600
2018	600
2019	600
2020	600