Year	% of land area
1961	20.467765390208434
1962	20.37081919534658
1963	20.067862336403298
1964	20.079980610761027
1965	20.116335433834223
1966	19.58313136209404
1967	19.389238972370336
1968	19.401357246728065
1969	19.207464857004364
1970	19.219583131362093
1971	19.231701405719825
1972	19.243819680077557
1973	18.347067377605427
1974	18.347067377605427
1975	18.310712554532234
1976	18.41977702375182
1977	18.528841492971402
1978	18.746970431410567
1979	18.45613184682501
1980	18.61366941347552
1981	18.771206980126028
1982	18.601551139117788
1983	17.438196800775568
1984	17.510906446921958
1985	17.54726126999515
1986	17.438196800775568
1987	17.438196800775568
1988	17.66844401357247
1989	17.680562287930197
1990	17.28065923412506
1991	17.510906446921958
1992	17.401841977702375
1993	17.19583131362094
1994	17.244304411051868
1995	17.135239941832285
1996	17.086766844401357
1997	17.03829374697043
1998	17.01405719825497
1999	16.989820649539507
2000	16.95346582646631
2001	16.808046534173535
2002	16.78380998545807
2003	16.723582161900147
2004	16.714735821619
2005	16.731701405719825
2006	16.689287445467766
2007	16.674745516238488
2008	16.58991759573437
2009	16.56083373727581
2010	16.526902569074164
2011	16.476005816771693
2012	16.421473582161898
2013	16.40693165293262
2014	16.380271449345614
2015	16.312409112942316
2016	16.29289869122637
2017	16.104459524963648
2018	16.082767813863306
2019	16.06313620940378
2020	16.056366941347548
2021	15.9932792050412