Year	mm per year
1961	78
1962	78
1963	78
1964	78
1965	78
1966	78
1967	78
1968	78
1969	78
1970	78
1971	78
1972	78
1973	78
1974	78
1975	78
1976	78
1977	78
1978	78
1979	78
1980	78
1981	78
1982	78
1983	78
1984	78
1985	78
1986	78
1987	78
1988	78
1989	78
1990	78
1991	78
1992	78
1993	78
1994	78
1995	78
1996	78
1997	78
1998	78
1999	78
2000	78
2001	78
2002	78
2003	78
2004	78
2005	78
2006	78
2007	78
2008	78
2009	78
2010	78
2011	78
2012	78
2013	78
2014	78
2015	78
2016	78
2017	78
2018	78
2019	78
2020	78