Year	mm per year
1961	534
1962	534
1963	534
1964	534
1965	534
1966	534
1967	534
1968	534
1969	534
1970	534
1971	534
1972	534
1973	534
1974	534
1975	534
1976	534
1977	534
1978	534
1979	534
1980	534
1981	534
1982	534
1983	534
1984	534
1985	534
1986	534
1987	534
1988	534
1989	534
1990	534
1991	534
1992	534
1993	534
1994	534
1995	534
1996	534
1997	534
1998	534
1999	534
2000	534
2001	534
2002	534
2003	534
2004	534
2005	534
2006	534
2007	534
2008	534
2009	534
2010	534
2011	534
2012	534
2013	534
2014	534
2015	534
2016	534
2017	534
2018	534
2019	534
2020	534