Year	% of land area
1961	53.125
1962	50
1963	46.875
1964	43.75
1965	40.625
1966	40.625
1967	40.625
1968	40.625
1969	40.625
1970	40.625
1971	40.625
1972	40.625
1973	40.625
1974	40.625
1975	37.5
1976	37.5
1977	40.625
1978	40.625
1979	40.625
1980	37.5
1981	37.5
1982	37.5
1983	37.5
1984	37.5
1985	37.5
1986	37.5
1987	37.5
1988	37.5
1989	37.5
1990	37.5
1991	37.5
1992	37.5
1993	37.5
1994	37.5
1995	31.25
1996	31.25
1997	28.125
1998	25
1999	25
2000	25
2001	28.125
2002	28.125
2003	29.062500000000004
2004	28.125
2005	25.624999999999996
2006	25.624999999999996
2007	25
2008	25
2009	25
2010	28.375
2011	28.375
2012	28.125
2013	28.031250000000004
2014	28.031250000000004
2015	28.031250000000004
2016	28.34375
2017	28.34375
2018	28.34375
2019	28.34375
2020	24.375
2021	24.375