Year	% of land area
1961	25
1962	25
1963	25
1964	25
1965	25
1966	25
1967	25
1968	25
1969	25
1970	25
1971	25
1972	25
1973	25
1974	25
1975	25
1976	25
1977	25
1978	25
1979	25
1980	25
1981	25
1982	25
1983	25
1984	25
1985	25
1986	25
1987	25
1988	25
1989	25
1990	25
1991	25
1992	25
1993	25
1994	25
1995	25
1996	25
1997	25
1998	25
1999	25
2000	25
2001	24.375
2002	21.0625
2003	20.25
2004	19.4375
2005	18.625
2006	17.8125
2007	17
2008	16.1875
2009	15.375
2010	14.5625
2011	13.750000000000002
2012	12.937499999999998
2013	12.125
2014	11.4375
2015	11.3125
2016	11.125
2017	10.9375
2018	10.875
2019	10.8125
2020	10.8125
2021	10.8125