Year	% of land area
1961	3.2
1962	3.2
1963	3.2
1964	3.2
1965	3.2
1966	3.2
1967	3.2
1968	3.2
1969	3.2
1970	3.2
1971	3.2
1972	3.2
1973	3.2
1974	3.2
1975	3.2
1976	3.2
1977	3.2
1978	3.2
1979	3.2
1980	3.2
1981	3.2
1982	3.2
1983	3.2
1984	3.2
1985	3.2
1986	3.2
1987	3.2
1988	3.2
1989	3.2
1990	3.2
1991	3.25
1992	3.35
1993	3.4000000000000004
1994	3.45
1995	3.5000000000000004
1996	3.55
1997	3.5999999999999996
1998	3.65
1999	3.75
2000	3.8
2001	3.85
2002	3.9
2003	3.95
2004	4
2005	4.05
2006	4.1000000000000005
2007	4.15
2008	4.2
2009	4.25
2010	4.3
2011	4.35
2012	4.3999999999999995
2013	4.45
2014	4.5
2015	4.55
2016	4.6
2017	4.65
2018	4.7
2019	4.75
2020	4.8
2021	4.8500000000000005