Year	% of land area
1961	47.44747476059925
1962	47.61768642074763
1963	48.55579954003872
1964	48.45445213933968
1965	48.45964944193963
1966	48.70392266413731
1967	48.464846744539585
1968	48.85594376518586
1969	50.209841092473006
1970	49.60565466522875
1971	49.78236295362707
1972	50.44761768642074
1973	50.39694398607123
1974	49.8005535127269
1975	49.325000324831414
1976	49.24834011148214
1977	49.412055143380584
1978	49.43284435378039
1979	50.53337317931993
1980	50.1266842508738
1981	50.17086132297338
1982	48.32322024869093
1983	47.708639216246766
1984	48.87153567298572
1985	49.54328703402934
1986	50.001948988474986
1987	51.22851240206333
1988	51.01542299546536
1989	51.83919545755753
1990	51.55334381456025
1991	52.06008081805543
1992	51.84829073710744
1993	51.85998466795733
1994	52.16662552135441
1995	51.31426789496252
1996	51.146654886114106
1997	50.98813715681562
1998	51.86778062185725
1999	52.36542234580253
2000	52.59540298585035
2001	53.230773228694304
2002	53.52701947689149
2003	52.80979171809831
2004	53.54521003599132
2005	53.562101269441165
2006	52.61359354495016
2007	51.32985980276237
2008	50.83221807881709
2009	50.5580603666697
2010	50.68929225731845
2011	49.695308135077894
2012	49.903200239075915
2013	49.92398944947572
2014	50.0942011096241
2015	50.090303132674144
2016	49.8005535127269
2017	49.327598976131384
2018	49.11710822083339
2019	49.00536621493445
2020	49.06513519483388
2021	49.490014682379844