Year	% of land area
1961	18.003260115233775
1962	18.231898559846783
1963	18.460537004459795
1964	18.691865313127074
1965	18.921848689767216
1966	19.149142202353094
1967	19.44502724832287
1968	19.740912294292645
1969	19.969550738905657
1970	20.308473609743764
1971	20.6447066165276
1972	20.980939623311436
1973	21.30103344576965
1974	21.855145440949414
1975	22.25862504909002
1976	23.132830866727996
1977	22.99833766401446
1978	22.863844461300925
1979	22.72935125858739
1980	22.66210465723062
1981	22.52761145451709
1982	22.325871650446786
1983	22.25862504909002
1984	22.19137844773325
1985	22.15372035097346
1986	22.10530279799659
1987	21.73813635458864
1988	21.72603196634442
1989	21.746205946751452
1990	21.383074299424905
1991	21.23513177644002
1992	20.92176261411748
1993	20.81551298397379
1994	20.779199819241136
1995	20.617807975984896
1996	20.48600463732563
1997	20.472555317054276
1998	20.46852052097287
1999	20.25467632865835
2000	20.32192293001512
2001	20.375720211100532
2002	20.9338670023617
2003	20.745576518562753
2004	21.43149185240178
2005	21.364245251045013
2006	21.249926028738507
2007	21.158470650893303
2008	20.665518094715495
2009	20.17256688346971
2010	19.678268050332736
2011	19.185315494154924
2012	18.692362937977116
2013	18.19941172673133
2014	17.706459170553522
2015	17.212160337416545
2016	16.719209126170764
2017	16.22625656999295
2018	15.733304013815141
2019	15.23900518067817
2020	14.746053969432385
2021	14.25027705599759