Year	% of land area
1961	21.14713216957606
1962	21.14713216957606
1963	21.14713216957606
1964	21.14713216957606
1965	21.14713216957606
1966	21.14713216957606
1967	21.14713216957606
1968	21.14713216957606
1969	21.14713216957606
1970	19.960099750623442
1971	19.860349127182044
1972	19.76059850374065
1973	19.66084788029925
1974	19.551122194513717
1975	19.45137157107232
1976	19.351620947630924
1977	19.261845386533665
1978	19.16209476309227
1979	19.06234413965087
1980	18.952618453865338
1981	18.952618453865338
1982	18.952618453865338
1983	18.952618453865338
1984	18.952618453865338
1985	18.952618453865338
1986	18.952618453865338
1987	18.952618453865338
1988	18.952618453865338
1989	18.952618453865338
1990	18.962593516209473
1991	18.962593516209473
1992	18.962593516209473
1993	18.952618453865338
1994	18.952618453865338
1995	18.942643391521198
1996	18.92269326683292
1997	18.902743142144637
1998	18.862842892768082
1999	18.8428927680798
2000	18.8428927680798
2001	18.8428927680798
2002	18.82294264339152
2003	18.802992518703242
2004	18.793017456359102
2005	18.773067331670823
2006	18.763092269326684
2007	18.713216957605987
2008	18.713216957605987
2009	18.703241895261847
2010	18.693266832917708
2011	18.685286783042393
2012	18.675311720698254
2013	18.675311720698254
2014	18.675311720698254
2015	18.673316708229425
2016	18.673316708229425
2017	18.673316708229425
2018	18.56590300505802
2019	18.56590300505802
2020	18.56590300505802
2021	18.56590300505802