Year	mm per year
1961	1168
1962	1168
1963	1168
1964	1168
1965	1168
1966	1168
1967	1168
1968	1168
1969	1168
1970	1168
1971	1168
1972	1168
1973	1168
1974	1168
1975	1168
1976	1168
1977	1168
1978	1168
1979	1168
1980	1168
1981	1168
1982	1168
1983	1168
1984	1168
1985	1168
1986	1168
1987	1168
1988	1168
1989	1168
1990	1168
1991	1168
1992	1168
1993	1168
1994	1168
1995	1168
1996	1168
1997	1168
1998	1168
1999	1168
2000	1168
2001	1168
2002	1168
2003	1168
2004	1168
2005	1168
2006	1168
2007	1168
2008	1168
2009	1168
2010	1168
2011	1168
2012	1168
2013	1168
2014	1168
2015	1168
2016	1168
2017	1168
2018	1168
2019	1168
2020	1168