Year	% of land area
1961	13.990937051637111
1962	14.036260966694522
1963	14.143618683780897
1964	14.19868635878742
1965	14.29806389238606
1966	14.353440193273322
1967	14.43346247520834
1968	14.456256700971648
1969	14.392371143658238
1970	14.492343884312593
1971	14.449422842183811
1972	14.53570582055672
1973	14.648972639898005
1974	14.643928167690015
1975	14.706327955506856
1976	14.728020070312837
1977	14.737455258460155
1978	14.838067872255381
1979	14.874022993442939
1980	14.806191045010005
1981	14.816402211247944
1982	14.971348281872446
1983	14.872922515423515
1984	15.018798460320605
1985	15.116635188855293
1986	15.08184844377009
1987	15.18453768075101
1988	15.184445092456107
1989	15.27813121999926
1990	15.240897498548748
1991	15.347398587738295
1992	16.230640166922363
1993	16.274294448302445
1994	16.334368020038323
1995	16.426267931651342
1996	16.395897281457074
1997	16.448112610275523
1998	16.481940647724812
1999	16.539839811825527
2000	16.455146346885975
2001	16.507119096781782
2002	16.518258718109134
2003	16.54643969698266
2004	16.521193556869466
2005	16.52460970696566
2006	16.544958225485285
2007	16.553648910307572
2008	16.570903182682606
2009	16.681528873395383
2010	16.61227185940264
2011	16.692766339072474
2012	16.717367889532674
2013	16.76662132712715
2014	16.75402534151495
2015	16.814795462880603
2016	16.89419528489136
2017	16.940398487647933
2018	16.957851821138796
2019	16.92296015555215
2020	16.961123984817682
2021	16.94192507935144