Year	mm per year
1961	89
1962	89
1963	89
1964	89
1965	89
1966	89
1967	89
1968	89
1969	89
1970	89
1971	89
1972	89
1973	89
1974	89
1975	89
1976	89
1977	89
1978	89
1979	89
1980	89
1981	89
1982	89
1983	89
1984	89
1985	89
1986	89
1987	89
1988	89
1989	89
1990	89
1991	89
1992	89
1993	89
1994	89
1995	89
1996	89
1997	89
1998	89
1999	89
2000	89
2001	89
2002	89
2003	89
2004	89
2005	89
2006	89
2007	89
2008	89
2009	89
2010	89
2011	89
2012	89
2013	89
2014	89
2015	89
2016	89
2017	89
2018	89
2019	89
2020	89