Year	mm per year
1992	533
1993	533
1994	533
1995	533
1996	533
1997	533
1998	533
1999	533
2000	533
2001	533
2002	533
2003	533
2004	533
2005	533
2006	533
2007	533
2008	533
2009	533
2010	533
2011	533
2012	533
2013	533
2014	533
2015	533
2016	533
2017	533
2018	533
2019	533
2020	533